reversed jumper cables damage

All of the dozens of computers have a diode built in to protect them. Diodes are one-way valves for electrical current flow. They are installed backward so they are turned off all the time, except when battery cables or jumper cables are reversed. Reverse polarity puts the diodes in the circuit so they are turned on and act like a short circuit. That is a temporary condition that is designed to cause the appropriate fuse to blow, thereby protecting the rest of the circuitry. Normally the only needed repair is to replace the multiple blown fuses.

When you have a fuse that blows repeatedly, something has become totally shorted. Given the history, we can assume the short is not due to a bare wire or other things associated with age or mileage. It is likely the protective diode shorted. I can repair things like that, but it is due to my TV repair background. For mechanics and auto repair shops, the fix is to replace the radio.

Be aware too there are multiple fuses for the radio. One of them is for the clock and station preset memory when the ignition switch is off, and that circuit is always tied into some other circuit that is always live, and is labelled for that circuit, not for the radio. Most commonly that memory circuit is tied into the interior lights circuit, but on some vehicles it could be the brake lights, cigarette lighter, or horn.

The white smoke could have been steam coming from water boiling out of the battery. At five years old, your battery is about to fail anyway and is due to be replaced. Reversing the cables is very unlikely to damage a fairly new battery, and for an old one, typically, at most it will simply hasten the impending failure. I would not get excited about a battery problem if it is time to replace it anyway.

The smoke could also have been caused by an overheating wire. In the past we had "fuse link wires" which were small sections of wire spliced in that were smaller than the wires they protected, so they were the weak link in the chain, and their insulation was designed to not burn or melt. They were used specifically because they needed some time to burn open. That prevented nuisance failures and the need for the rather involved repair procedures. Fuse link wires were expected to last the life of the vehicle and were only needed for catastrophic failures. Since the mid 1990's, most vehicles use large plug-in fuses now instead of fuse link wires. Each of those protect multiple circuits that each still have their own smaller fuses. Usually those smaller fuses blow so there is no need for the large ones to blow. For that reason, when you have multiple things that do not work, it is more likely you'll find many small blown fuses and not one large fuse.

Be aware that the insane engineers have seen fit to hang an unnecessary computer onto every part of our vehicles now, and there is absolutely nothing you can name that does not have one involved. We have tire pressure monitors, (computer), heated seats and steering wheel, (upholstery / computer), heated window and mirror defrosters, (computer), and dozens more. Every one of those computers do multiple things. You should check each of those things you can identify. For example, it is critically important that dome lights fade out slowly rather than simply turn off with a switch. That means those lights are run by a computer. Door locks used to work just fine with switches. Now they are run with a computer so you can open just the driver's door or all four doors with a remote. Be sure all those functions are working correctly.

There will be some things you may need to reset to your preference, like radio stations, instrument cluster settings, and things like that. There are also some things you will need to make happen, like running an electric radiator fan. Hopefully your mechanic will check as many of those things as he can think of. That includes dash warning lights that are supposed to turn on for a few seconds when you start the engine, while those computers are running short self-tests. For example, the Check Engine, Air Bag, and Anti-Lock Brake lights should all turn on for roughly six seconds, then they must turn off and stay off. It is very unlikely circuitry associated with those computers would be damaged by reverse polarity, but that is part of what those computers test each time you turn on the ignition switch. If any warning light fails to turn on for a few seconds, or stays on while driving, given the recent history, suspect the computer, not the rest of the wiring.

Ask to have the cause of any damage and repairs documented on the repair order and the final bill. Mechanics are supposed to write their "story" on the back of the repair order. That is what is used, in part, to calculate their paycheck and your bill. Repairs that are listed in the "flat rate" guide are billed according to the amount of time the job is supposed to take, regardless if the mechanic takes longer or gets done quicker. With this type of repair when there is no way to know what is involved in diagnosis or repair, the bill is based on the actual time the mechanic is on the job. He can't lose money by being inefficient, but he cannot earn extra money by investing in expensive tools and advanced training, or by working as efficiently as possible. For this reason, an experienced mechanic is going to want to solve all the problems as quickly as possible so he can move on to other cars where he has the potential to earn more money. The checks and balances is if he overlooks something and you return to the shop, he is going to have to drop what he is doing and go back to your vehicle. He wants to avoid that, so while he wants to get everything found and solved as quickly as possible, there is an incentive for him to take his time and do it right the first time.

Related to this documenting the suspected cause of the failure, be aware a lot of people will try to get things repaired that are not related to the reversed jumper cables. The first thing to consider is your battery was run down after running the radio for just ten minutes. I just replaced the battery yesterday in my Grand Voyager. It had been running my laptop computer for fewer and fewer minutes all summer, and yesterday was the first day it got down to below twenty degrees, (low temperature is a killer for old batteries), and it would not start the engine. I knew the battery was on its last legs for months, and it would not be fair to make someone else pay for a new one. You are already fortunate to be working with a towing company that is ready to pay for their mistake. Your battery was about to fail anyway so don't balk if they do not want to cover that.

I have actually spoken with people who think they can sneak in tires and alignments, and oil changes, as being needed because of someone's mistake. Honest shops and mechanics will not do that. They will look out for the towing company just as they will for you.

Please do not be angry if you do find something that got overlooked. This could turn out to be a simple repair, as they usually do, or it could become quite involved. Shops and mechanics hate it when you have to return for the same problem, so they are going to try to avoid that, but these cars are extremely complicated. You can help by listing as many non-working things as you can remember when you talk with the service writer.

Hi Cardiodoc, thank you for your quick and thorough answer. Yes, I agree that my battery is old and was likely on the way out, so I would not be upset if the tow truck company did not pay for a new one, although reversing the jumper cables most likely shortened the life. However, I am thinking it would be reasonable for them to cover the cost of replacing the cables if the diagnostics indicate they are damaged. There was no visible corrosion at the terminals and the cables appeared to be in good shape prior to the mishap (no sign of cracked plastic etc). You mentioned that several computers should be checked for damage. Would that include the ECU, PCM, and CKP? Could those have been damaged by the mishap? How about the alternator, starter or solenoid? I have read several posts on several troubleshooting websites that suggest these could possibly be damaged by reverse polarity or would the fuses and fusible links and diodes blow first in order to prevent any damages to the above items? Any additional comments would be appreciated. Thank you for your help!

The ECU, (electronic control unit / engine control unit), and PCM, (power train control unit), are the same thing. GM typically uses "ECU", and Chrysler uses "PCM". If the engine starts and runs normally, the PCM is likely okay. It controls a real lot of other stuff, but not until it is powered up. One of those things is the CKP, (crankshaft position sensor). That is part of the external wiring for the PCM and is not going to be damaged. That sensor has to work for the engine to run.

Do not even think about starter trouble. The motor can run backward without being damaged. That does not mean it will crank the engine backward. It just means an electrical motor of this design doesn't care about polarity. Same with the solenoid built into the starter motor. It is just a big coil of wire, and it will operate with either polarity.

The alternator is a different story. They were actually developed by Chrysler for use in 1960 models, and Chrysler copyrighted the term. (Little piece of useless trivia). Today, to standardize terminology, we call them "AC generators". Electrical power can only be stored chemically in a battery, and those only store DC power. The alternating current coming out of the AC generator has to be converted to direct current, and that is done with six internal diodes, those one-way valves for electrical current flow. Unlike when they are used for protection in computers, in the alternator they are installed so current goes through them, then out to the battery and the car's electrical system. They perform a second desirable function of blocking current flow from draining the battery when the engine is not running, (and the alternator is not producing output current). These diodes are really beefy and tough. It takes a lot to destroy one, but it does happen at times. When the alternator is working, it will generate roughly 20 to 50 amps, whatever is needed to run the electrical system and recharge the battery. It is capable of developing a lot more current, up to its design value, which can be well over 100 amps. When the battery cables are reversed. those diodes are no longer in the circuit backward and turned off to block current flow. They are "forward biased" and will act like a dead short. I mentioned those fuse link wires that were used on older vehicles. On one as new as yours, there is going to be a really large fuse bolted into the under-hood fuse box. That fuse should blow before a diode gets hot enough to short.

Your mechanic should perform a charging system test. It only takes a couple of minutes. In particular, I would like to see what is found for charging voltage, "full-load output current", and "ripple voltage".

Those diodes are in two sets of three. Any one diode in each set has to short for there to be a direct short. A somewhat common failure is for just one diode to short, then the excessive heat usually causes it to burn open, meaning it is like it is not even there in the circuit. That removes the potential for a dead short to occur if a second diode shorts, but it causes a more immediate problem. I looked up a replacement alternator for your vehicle. It came with either a 140-amp or a 160-amp alternator. (That is huge. Years ago a large, optional unit might be in the 55 to 65-amp range). Without going into all the electrical theory, all we need to know is when one diode fails, the most the alternator will be able to develop is exactly one third of its rated maximum current. The only time any alternator will develop its maximum current is during the full-load output current test. It will never do that while just running the vehicle's electrical system. The reason we do this test is to determine if there is a failed diode. The test takes the better part of three or four seconds once the tester's cables are hooked up.

When a diode has failed, one out of every three output voltage pulses is missing, and system voltage will drop slightly. This is getting too technical, but this is what is being measured with ripple voltage. A few testers will display it as a voltage, but most just show whether it is low or high. They show that on a bar graph that lights up. We want to see low ripple voltage. If you're lucky enough to get a printout with the numbers, list those numbers here and I will interpret them. If you see anything close to 130 to 140 amps, or more, for output current, the diodes are fine. Ripple voltage at that point will be irrelevant. Every time I performed this test, I wrote the numbers on the back of the repair order. It was up to the service writer whether he wanted to enter that information into his computer to show up on the invoice. You can request a hand-written list of those numbers if that is what it takes.

Be aware because of its physical properties, an alternator is incapable of developing more current than it is designed to produce, and they do not get weak and develop only slightly less than what they were designed for. That means if you find 140 amps during the full-load test, you have a good 140-amp alternator, not a weak 160-amp unit. If you have a 140-amp alternator with a bad diode, the most current you will get will be close to, uhm, lets see, about 45 amps. That is enough to run the engine and electrical system, but not under all conditions. At times the battery might have to make up the difference, and that can cause it to slowly run down over days or weeks, especially if you do a lot of slow and short-trip driving.

The battery cables are not going to be a concern. They need to pass over 200 amps to run the starter motor. You have to remember that while the jumper cables were reversed polarity and trying to make current flow the wrong way, your battery was still connected properly and was fighting the current from the jump-starting vehicle. The damage is going to be less than when someone is installing a new battery and connects the cables backward. There was probably more stress on the jumper cables than there was on your battery cables.

Thank you again Cardiodoc. U da bomb! I will be sure to bring up all these issues and make sure the dealer has checked them. If I can get a list of numbers I will share them with you. Hopefully I will hear back from the dealer in the next day or two and will give you an update at that time. Again, thank you for sharing your expertise. If I do not hear back before Thanksgiving, I would like to take this time to wish you and your loved ones a wonderful holiday!

Thank you. I have to drive ten miles into town to sit in the library parking lot to use their wireless internet, and in the winter I do not do that every day, so do not panic if you do not hear back from me right away. Will wait to see your numbers.

:)Thank you. Will be in touch. Stay warm :)

Well, Cardiodoc, I just got an update on my car. They have to replace the power module, that is what they called it. they said the whole fuse box is toast. They said the alternator is fine, although they did not give me any amp readings. I will push them on that. I asked if it was reading around 140 amps and they said "yeah it appears to be charging the battery and doing what it is supposed to do." They also said the battery appears to be holding a charge but they will check that again tomorrow. The power module will be installed tomorrow so they will know more after it is installed.

Dandy. Push for the full-load output current. Remember, that test only takes a few seconds. It takes considerably longer to wheel the tester to the vehicle and connect the three cables.

"Charging the battery okay" is like saying the water supply to your house is okay because you are getting enough water to brush your teeth. You may at times also want to do a load of wash or take a shower. You wont be happy with that little trickle of water.

Thank you. I will push for the full-load test. About the battery, what kind of charge would be good/acceptable?

You do not need to be concerned with the battery's rate of charge. He will take care of that on his own. Typically, right after cranking the engine and running the battery down, it will accept a charge rate of around 20 amps, but that will quickly drop to ten or less. We consider a battery to be fully-charged when it drops to five amps or less.

If you are interested, I used water analogies with my students to make electrical theory easier to understand. Think of the municipal water tower in your town. The weight of the water in it is what creates the pressure in the pipes. Voltage is electrical pressure, but just like water sitting in the tower doesn't do any work, 12 volts sitting in a battery does not do any work either.

Once you connect some pipes and open some valves, you give the water a place to flow to. That is current flow. If you connect a rotating lawn sprinkler, that current flow will cause work to be performed, spinning the sprinkler.

Once you connect some wires and turn on some switches, you give electrical current a place to flow. If you connect a motor, it will spin, or a light bulb will light up.

Now, if you use up half of the water in the tower, you'll have less weight, and less pressure. With half the pressure, the lawn sprinkler will spin slower. We need to refill the tower to get the pressure back up, and that is done with a pump.

There is a noticeable difference when talking about the car battery. A fully-charged battery will measure 12.6 volts. When it is almost completely used up, (run dead), it will still measure around 12.2 volts, but that is enough for us to use as a gauge. Refilling the battery will raise its voltage very little, but it will seriously increase its ability to do work. We refill it with current from the alternator.

Here is where my sad story gets horrendously exciting. If you have fifty pounds of pressure in the water tower, but only fifty pounds from the pump, there is no incentive for any water to flow up into the tower. You need to have considerably higher pressure from the pump to recharge" the tower.

Likewise, you need a higher voltage from the alternator to convince current to flow into the battery. The magic number is between 13.75 and 14.75 volts. With that voltage, current will flow fast enough to quickly recharge the battery, but not so fast as to overheat the plates in it. I mentioned those diodes in the alternator already, and that if one is bad, you will only be able to get one third of its maximum rating during the full-load test. With that reduced current capacity you will still find the charging voltage to be between 13.75 and 14.75 volts. This is why simply measuring battery voltage with the engine running will tell you if the alternator is working, but it won't tell you if it is working to its full capacity. You can use an inexpensive digital voltmeter to measure the charging voltage yourself, but finding an acceptable voltage only means it is okay to perform the rest of the tests, meaning full-load output current and ripple voltage, and you need a professional load tester to do that. This is why I do not want you to accept, "it's charging the battery okay". The quick and easy voltage test will appear to be okay even if the alternator has a bad diode. We want to now the full-load output current.

As a point of great value, if you have to insist on seeing the full-load test performed, the mechanic might be on another job and will have to stop what he is doing. Most of us are happy to do that, especially when we just got done working for a paying customer, and we like to show off our skill and knowledge, but there are always the few of us who become crabby or irritated. You might consider returning a few days or a week later with a box of donuts or cookies as a "thank you". At the dealership I worked for, we had treats like that almost every week from happy customers. (Chocolate chip cookies are our favorite)!

I am definitely pushing for a full-load output test, Especially in light of the burned up ECU, or power module as they called it. They said they have to install the new one first, then will run tests on everything. I also requested the mechanic write down the values from the testing. And as annoying as it might be to them, I have requested they check everything that takes electricity (they said they would) and to please document what they did: radio, CD player, speakers, clock, dome light, lights (headlights, brake lights etc), wipers, door chimes (when lights are left on or key in ignition), all door locks, power windows, alarm, heater, A/C, and make sure the dash warning lights light up upon ignition and then go off. Also need to check the axle lock and sway bar toggle switches (I have a Rubicon). If they are not willing to do all that then I will do it myself before I sign anything or before I drive off the lot. And then I will bring them chocolate chip cookies (homemade)!

Dandy. Remember too that ninety nine percent of electrical stuff is run by or is an input to a computer. None of that is going to be damaged. Even if the computer related to those circuits is damaged, it will not cause further damage down the line.

I understand too their comment about having to replace a computer before further testing can be done. I have a 2014 truck that wont even let me turn on the high-beam head lights unless the engine is running. I am sure the insane engineers had some reason for designing it that way, but I will never figure it out.

I understand. I just want to be thorough. As I mentioned in my initial post, after the reverse polarity mishap, the radio and clock were dead, and so were the dome light and the door chimes probably just blown fuses and the new PCM should take of that. When I get those test numbers I will post them here. Thank you again Cardiodoc, you are the greatest!

Oops, just realized I have been spelling your name incorrectly! It is Caradiodoc! I am sorry about that :)

That's okay; I know who I am!

Library just closed and I'm sitting in my freezing van. Their wireless is not working real well tonight in the parking lot. I'll check back tomorrow to see if there's any progress.

Okay, thank you!

Just thinking ahead, if I do need a new battery, I did a tiny bit of research on batteries. What do you think of Interstate Mega-Tron Plus. 730 CCA and a 6-yr warranty? If the tow truck company will not cover the cost, could I install it myself with a wrench? Will any codes be affected in the process? BTW, I would bake you chocolate chip cookies if I could but I doubt you are local. And one more question; if I make a donation to this website, do you receive any percentage of it? I am a broke starving student, but I realize when I have received a gift, gift of your knowledge and expertise, and I hope a donation would compensate you in some way.

Hi Caradiodoc. They installed the power module this morning but the radio still does not work. They think there is a short in the wiring to the amplifier--they are looking into that and will resolve it first before moving on to the next checks. The mechanic said that the big fuse to the alternator was not blown so he does not think there is any damage to the alternator, but I still insisted they do a full load test. I don't have any numbers to share yet. I might get another update from the dealership today before they close, but if not, then I will not hear back from them until Sunday--they will be closed for Thanksgiving.

Just got another update. The mechanic is still tracing the problem with the stereo. I definitely won't get my jeep back before Sunday, maybe not even then. They do plan to test the alternator (full load test) as soon as they can get to it. I asked them if the tow truck company was going to pay for a new battery if I needed one, and he said "Oh yeah." So far so good. I will give you another update on Sunday. Happy Thanksgiving!

I'm in the middle of Wisconsin. As for dollars, the web site owners do compensate me for every answer of value I submit. I used to get a portion of donations, but I don't know if that is still the case. Regardless, donations are greatly appreciated by the site owners as it is expensive to run a web site. I really like it that donations are not required.

I have a web site of my own and I just got another bill. I'm in the process of moving it to another company or just discontinuing it due to the cost. It jumped this year to over $500.00. I just spill automotive electrical information for students and instructors. I don't sell anything and I have never made a single penny on advertising.

As for batteries, I cover that on one of my web pages. To boil it down to the basics, the lead flakes off the plates over time. There is no way to avoid that, but the manufacturers know how quickly that will occur, and they use that information to provide the longest warranty period possible because that translates into more dollars they can charge for that battery. There is an area in the bottom of the battery's housing where that flaked-off lead accumulates. When it builds up high enough, typically after five years, it will short the negative and positive plates in that cell together. At that point the battery must be replaced. It will crank the engine very slowly, if at all, and if it does, it is usually too slowly for the engine to start. Even a jump-start might not work at that point because the shorted cell is still shorting out the jumping battery.

A battery can also fail before that lead builds up in the bottom of the housing enough to short the plates. The lead needs to be suspended on the plates, in the acid, to work. When half of it flakes off, the battery may still crank the engine just fine, but not for as long. A better example is when you leave your head lights on, (in the days before we had computers that turned them off for us). A fairly new battery would run those lights for about two hours before it was run down to the point it wouldn't crank the engine. By the time it's three years old, it might only run those lights for an hour, due to the less lead in the plates and therefore less room to store electrons, but it can still provide short bursts of very high current to crank the engine. I just went through this a few days ago with my van. I use a little power inverter to run my laptop when I sit in a parking lot using someone's wireless internet. Last spring I could run it for two hours or more, then start the engine and drive home. Last week it was down to less than a half hour, then, when it suddenly got cold the next day, it wouldn't even crank the engine fast enough to start. Electrical power can only be stored in a battery, and that is done chemically. Chemical reactions always slow down as temperature goes down, plus, cold engine oil gets real thick making the engine harder to crank. We need more cranking power and we're trying to get it from a battery that is weaker. That is why most battery damage occurs in hot weather, but it shows up in cold weather.

Here's the clinker. To be able to offer the longer warranty, which will cost extra, that area in the bottom of the housing that collects the flaked-off lead needs to be bigger. That means there's less room for the plates, so they have to be smaller. That isn't such a concern today when fuel injected engines start right away. Back in the '60s and '70s, with carburetors that were out-of-adjustment, it wasn't uncommon to grind on a starter for much longer before the engine finally started, especially on cold winter days. We needed batteries with plenty of lead in the plates to give us that longer cranking time.

You have to decide if the longer warranty is worth the extra expense. Only a very low percentage of any batteries fail during the warranty period. Instead, look at the length of the warranty as an indicator of how long you can expect that battery to last. Often they will fail with just a coupe of months left in the warranty. I've always been suspicious that was planned because the only way to collect on that is to receive a tiny discount on the cost of a new battery, . . . from the same manufacturer. I look at it as a low-cost way to get you to buy another one of their batteries. Of course, to be fair, there are a lot of batteries that last considerably longer than their warranty period.

A few years ago I bought the cheapest Carquest battery I could find. That lasted over eight years, but now I found a better alternative. We have a battery store in my town that sells "reconditioned" batteries, but they don't advertise that, or tell you about them. You have to know about them and ask for one. One time they told me they were called "reconditioned", but they simply had been sitting on the shelf for over a year and they wanted to get rid of them. Another time they told me, as I had originally suspected, someone bought the battery, took it home and installed it them self, then found out it didn't solve the problem and they returned it. Technically it is now a used battery and can't be sold at full price.

Currently this store is selling their reconditioned batteries for $30.00 exchange. I always have a bunch of old batteries laying around. They buy them for six bucks each. Each time I need a battery, I take them six bad ones, make an even exchange, and only have to pay the sales tax.

You can also get some good deals at the larger salvage yards. The smaller yards typically buy the older cars where people keep the batteries, or they're on their last legs. The large yards buy late model insurance wrecks that are often one to three years old. They will often have more fairly new batteries than they know what to do with. My local yard sells them for $19.99.

There are a few Chrysler models that have gone to the really miserable side-post batteries that GM refuses to give up on, but I think your Jeep uses the better top posts. If so, when you look for a replacement battery, look at which corner the positive and negative posts are in. Match the new battery to that to be sure the cables will reach. Anyone at a battery store or salvage yard will know right away or they will pop your hood and look to be sure. You can replace the battery yourself, but there are some things you must be aware of. First of all, many of the computers have memories that will be lost. For example, you'll need to reset the clock and your favorite radio stations. Any diagnostic fault codes stored in the Engine Computer will be lost. That isn't a big concern, and will have occurred anyway during the current repair work. Fuel trim data will start to be rebuilt as soon as you resume driving. That takes just a few minutes and you are likely to not even notice the less-than-perfect engine performance.

What DOES worry me is there are some European import cars that have multiple computers that lock up when the battery is disconnected or run dead. That requires a very expensive tow to the dealership. GM copied that idea since they are the top manufacturer at coming up with innovations that benefit them at the expense of their customers. (Chrysler has always been the leader, since the '50s, at developing innovations that really benefit car owners, but that's a story for a different time). To avoid these problems, there are a number of "memory saver" devices on the market. Most of them plug into the cigarette lighter and use a 9-volt transistor battery to keep the computer memory circuits powered up. I use a small battery charger hooked right to the battery cables, but there are certain precautions that must be observed when doing that. I do have a 2014 Dodge truck that was smashed, and my friend rebuilt in his body shop. We did need to disconnect the battery a few times, and there was not a single indication that was done other than the incorrect clock, so I might be worrying you about nothing. You can ask your mechanic if any computers need to be unlocked after reconnecting the battery. If he says "no", you can overlook this entire paragraph.

Along with the location of the two posts on the battery, the positive post is always larger in diameter than the negative post. Use your wrench to loosen and remove the negative cable first. We do that one first only because if you slip and the wrench contacts the clamp and the body sheet metal at the same time, nothing will happen. The two are actually connected together by the smaller wire on the negative cable. If you do the positive cable first and the wrench makes contact with another metal part, there will be huge sparks, and the wrench can actually get welded in place and become red hot enough to melt and bend! Remove the positive cable last. That way, if the wrench makes contact with a metal part, nothing exciting will happen. No current can flow and cause sparks once the negative cable is already disconnected.

There will be either a bolt to loosen to loosen the hold-down bracket near the bottom of the battery, in front or in back, or there will be a strap-type bracket over the top. Once you get the new battery in, be sure whatever is used to hold the battery in place is tightened properly. If it is not, the battery will vibrate excessively. That will aid the lead in flaking off the plates, and will shorten the battery's life.

Use a post cleaner to scrape the inside of the cable clamps and the outside of the posts so they're clean and shiny and make good contact. Don't get so carried away that you grind off so much that the clamps can't be tightened enough. What you don't want to see on the contact areas is a hard black coating. That is one type of corrosion that prevents a good connection.

As a point of interest, don't let anyone sell you a pair of "juicy rings" that slide over the posts to prevent corrosion. What I have found is when a lot of the lead has flaked off the plates, as in when the battery is near the end of its life, the little lead that is left has to absorb the full charging current flow, and that makes the plates get hotter than normal. The heat causes increased gasing and bubbling of the acid, and those bubbles reach the underside of the top of the housing. From there, the acid that has splashed onto the case works its way over to the posts where it sneaks through the mechanical joints and collects right under the cable clamps. That is what causes the white corrosion that looks like cauliflower. If that corrosion hasn't shown up yet on an old battery, those juicy rings aren't going to do anything. If the corrosion has shown up, the battery can be expected to fail within the next six months, and the juicy rings aren't going to change that. When I saw that corrosion on a customer's battery during other services, like oil changes and alignments, I would include a written warning on the repair order, to expect a failure soon. Some people thought I did something to their battery to cause the failure, and that's how I knew it was going to fail.

Reconnect the positive cable first, then the negative one. The positive post, as I mentioned, is larger, it has a plus sign molded into the top right next to it, and often there will be red paint on the top of the post. The negative post is smaller, has a minus sign next to it, and when used, will have green paint on top. If you mistakenly try to put the negative cable on the positive post, it won't fit unless you spread the clamp open. That is the first clue you're about to do the same damage that is being repaired now. If you put the positive clamp on the negative post, it will be too loose.

My experience has been that computers with "customer preference" settings retain their programming when the battery is disconnected. Those settings include things like horn chirp when locking the doors with the remote, speed-activated door locks, and things like that. Tire size is programmed into the Transmission Computer so the speedometer will be calibrated correctly. That should not change, but to be safe, observe if you're going faster or slower than everyone else. I check my vehicles with the remote radar signs the cops set out periodically. Those seem to be pretty accurate.

Wow, I had no idea changing a battery was so involved nowadays. Don't remember it being such an ordeal back in the 70s. Everything is so computerized now I guess it is to be expected. Good news is, according to the dealership, the tow truck company is prepared to pay for a new battery and install if needed. If for some reason they do not compensate me, your answer makes me feel confident that I could do it myself, but in that case I will check with the dealership first--I don't want to invalidate any remaining warranties or have to take the jeep in to have some codes reset--just more hassle. FYI, I live in a small town in So. Oregon, about 15 miles away from the dealer and grocery stores and doctors. So I don't like to make any avoidable trips into town--my Rubi is not very fuel efficient since I had the lift kit and larger tires installed a year or so ago :) And, unfortunately, I cannot afford to drive to Wisconsin to bring you cookies, so I will make a donation to the website. How much I am not currently sure, because I don't know how much out-of-pocket expense I may have because of this unfortunate mishap--hopefully no out-of-pocket. Regardless, I will donate what I can afford.

As I mentioned, the mechanic is still troubleshooting the stereo system, and has not gotten to the other tests. And as they are closed until Sunday, I will not have any updates until then. This is excruciating being without wheels for so long, but I am a patient person and I want them to check every important thing that may have been damaged from the reversed polarity--I don't want to get stuck with a bill later for some undiscovered damage that was likely caused by this. Thank you for getting back to me. I will keep you posted. Thank you for all your help!

Please let us know happens so it will help others. Nice work Caradiodoc!

Best, Ken

Yes, excellent work Caradiodoc! I'm still waiting to hear an update from the dealership. No mechanic available until tomorrow Sunday due to Thanksgiving weekend. My jeep is still in the shop (it will be 8 days tomorrow, without a loner); last update was they were tracing a bad wire to the stereo system, and had not yet run a full load output test, which will tell me if the alternator was damaged from the reversed cables. I still do not know what out of pocket expense I will have to shoulder: hopefully zilch. As soon as I know, I will know how much of a donation I can make to the site.

Caradiodoc I will post another response as soon as I can get back in touch with the dealership. Thank you so much for your help!

Hi Ken, how do I make a donation? FYI, I am still waiting for update from the dealership.

Hi Caradiodoc. Well, my Jeep is still at the dealership. Today they finished tracing the problem with the radio--the amplifier is blown and is on backorder for a month--tow truck company is paying for this repair. They also tried to perform the full load test but could not do so because my battery will not hold a charge--they are awaiting approval from the tow truck company to cover the cost of a new battery. So, I still don't know if there was damage to my alternator. Hopefully will know more tomorrow.

Sounds good, please let us know.

Caradiodoc, are you available? I have some numbers for you. The dealership mechanic replaced my battery and then hooked it up to their professional testing tool which is made specifically for Chrysler (not a voltmeter or multimeter). The test took 56 minutes, and it does not provide amperes. It gave a charging voltage at idle of 14.6V and loaded it was 14.55V. The ripple voltage was 23mV. And it also gave a statement something to the effect of "No problems" indicating no problems with the alternator/generator. I asked them to run an additional test with a voltmeter set to "AC Voltage" and hook it up to the battery and rev the engine up to about 1500rpm (based on what I read on the internet on how to test for diode damage with a voltmeter), and asked them to provide me with that reading. According to that website, the voltage should read 0 if no diode damage, and if it reads ANY voltage, it means there is a damaged diode. If the voltmeter reads 0, can we assume the alternator does not need replacement?

FYI, their testing tool is a big thing on wheels and has cables you hook up to the battery I guess, maybe also the alternator.

Another update, Caradiodoc! One of the technicians had an amp meter at home, ran home at lunch to get it. They hooked it up to my jeep, and the reading was 119 amps. My alternator size is 120 amps, so it sounds like the alternator was not damaged. The dome light still does not work (i.e. it does not come on when you open the driver's door); the dealership says that is tied to the stereo amplifier, and should work once the damaged amplifier is replaced (it is on backorder). They are going to note in the paperwork that they cannot check the speakers until the new amplifier is installed, and additional repairs to the speakers may be necessary if they don't function once the amplifier is installed. They said the door chimes work, the alarm works, the door locks work, the other lights work, the horn works, the panic button works. I will check some other things when I go to pick it up but all seems to be good now!

So, here is a list of currently known damages to my Jeep resulting from the reversed jumper cables:

Blown TIPM
Damaged battery
Damaged amplifier

The towing company has agreed to pay for all the above damages! Yay!

Nine days without a vehicle (towing company did not offer to pay for a car rental, nor did I push for one)

Thank you very much Caradiodoc for your help and expertise!!!

Good to hear, please use 2CarPros anytime we are here to help.

Best, Ken

I absolutely will! Thank you so so much!

The speakers are fine. It is possible, but extremely rare, for an amp to damage a speaker, and to do that, it has to be turned on. It will never turn on with reverse polarity or with a blown fuse.

My limited research showed your vehicle came with either a 140-amp or 160-amp alternator, but even a 120-amp is huge compared to what we had even a few years earlier. I never heard of measuring AC voltage to test for a defective diode, and I'd have to experiment with that to see what to expect. Digital voltmeters are only designed to be accurate when measuring 60 cycle sine waves, which is house current. The AC ripple that all alternators develop is much faster than 60 cycles, even when the engine is idling, and is not a nice clean sine wave. That doesn't mean the meter won't read anything, but I don't think it should read "0". Some ripple voltage has to be expected, but it should be low, as in 0.23 volts. Most testers only give a relative indication between "low" and "high" because the actual value s not important. Regardless, the only way you can get 119 amps is to have a good 120-amp alternator. Given the range of production tolerances, I'd be happy with 110 amps if this was from a 140-amp alternator. As I mentioned previously, with one failed diode, the most you would get from a 120-amp alternator is 40 amps.

Without perusing a wiring diagram, it sounds like the amplifier gets a turn-on signal from the radio over the vehicle's data buss, and it has a constant 12 volt feed for its power source. I've never worked on an amp of that style, but I know the newer radios work the same way. The radios always have a similar constant 12 volt supply, and that is always tied into some other circuit that is always live. That could be the horn, the brake lights, on some cars, the cigarette lighter, but by far the most common is the interior lights. In the past, cars had one fuse labelled for the radio, and you just had to know the second radio fuse was labelled "interior lights". The rather obvious clue when that fuse was blown was the interior lights didn't work! I'm wondering why the amp is needed to make the lights work if it's just a blown fuse, but I'm not going to second-guess someone who appears to know what he is doing, especially since I've never worked on these circuits.

As I mentioned earlier, your battery was just about at the end of its life, as evidenced by the fact it would not start the engine after running the radio for just ten minutes. If the company is going to pay for a new battery, it sounds like they have your best interest at heart, as most companies do. Reversed jumper cables can not damage a good battery. The jumper cables would overheat and melt first. Remember, the battery needs to deliver often over 250 amps to crank an engine, and they can do that for quite a while. Two batteries, connected together incorrectly with jumper cables, will not pass 250 amps because the clamps just don't make a good enough connection. I would look at this as you're getting a battery the towing company shouldn't have to pay for, in exchange for the car rental it would have been nice if they had paid for.

Plus, . . . you got to visit us and learn way more than you wanted to know! :)

Hi Caradiodoc! Thanks for getting back to me. My Jeep engine was off when I got the jump, but I don't remember if I turned off the radio before I turned off the engine (remember, I had my ignition key turned to accessory and was listening to the radio, then tried to start the jeep and it wouldn't start--I don't remember if, at that time, I turned off the radio before I turned the ignition key to off and waited for the tow truck). Would that have made any difference--i.e. would it have damaged my speakers? I'm guessing not.

The interior lights stopped working after the jump (dome light, power window lever illuminators, climate control dial illuminators), and when I turn on my blinkers the rear ones work fine but the front ones do not--what happens instead is the fog lamps blink. The dealership said that the above issues are programming issues (they had to reprogram everything when they replaced the TIPM but cannot reprogram the amplifier until the replacement gets here and is installed). They said the interior light problems and the blinker problems should be resolved once the amplifier is installed and reprogrammed. Does that sound right?

I was surprised when they told me I only had a 120amp alternator. Regardless, it is putting out 119amps and as you said, even if I had a 140amp alternator, a value of 119amps would be acceptable.

I was happy the towing company paid for a new battery--that was generous of them and I appreciate their generosity. I hope they appreciate that I did not insist on a car rental for 9 days :)

Hmmm...I just did a quick search online and there are a host of posts about TIPM issues, including interior light issues and fog lamp/blinker issues. One post in particular reads as follows:

"2011 Jeep Grand cherokee fog lights flash when turning right blinker on:
This has been common after replacing the TIPM. The TIPM circuits for the turn signals and fog lamps have been revised. Once the TIPM has been replaced the wiring needs to be relocated for proper operation. You can see the information from Chrysler HERE. Please view the procedure and relocate the wiring for proper operation."

Well, I tried to click "HERE" but got an error message. So I called my Jeep dealer and told him what I read online. He will consult with the mechanic and will get back with me. I will let you know what they say.

Please let us know happens so it will help others.

Best, Ken

Okay, the dealership confirmed that on the new TIPMs you have to switch the pins during installation because the wiring orientation for the blinkers and foglamps has changed (you have to reverse the pins--put the pin to the blinkers into the slot for the foglamp pin and vice versa). Sorry for the crude explanation but you tech/mech guys probably know what I am trying to say.

Yep, thanks for the update so everything is working correctly now?

No, I have to make an appointment to get that issue with the blinkers resolved, so maybe early next week they can fix the issue. The amplifier is still on backorder, so I won't know anything more about the interior lights issue until they install the amplifier (because they said the two issues are related somehow)--could be days, could be weeks before that part is available for install. I will let you know as soon as I know--I hope it's soon--it's hard to see at night without the interior lights and boring to drive without music :)

Hey Caradiodoc. About your comment "I'm wondering why the amp is needed to make the lights work if it's just a blown fuse"; maybe they are correct in saying they cannot finish programming the TIPM until the amp is replaced, but that explanation just sounds weird. I have been searching the internet trying to figure it out, and the only thing I could find was reference to the IOD fuse (ignition off draw). The fuse is contained in a small white fuse box inside the TIPM, and is pulled out at the factory prior to shipping the vehicle to the dealership, in order to reduce draw on the battery during shipping/storage. The dealership then re-inserts it prior to sale. There is also mention of this in the 2011 Jeep Wrangler manual--if an owner plans to store their Jeep for a month they should first pull out this little fuse and keep it somewhere warm and dry while the vehicle is in storage. I just wonder if that fuse box was firmly inserted upon installation of my new TIPM. Some online posts state that it can be partially disengaged to the first dentent and the vehicle still start, but the radio or interior lights may not work. I have not looked under my hood since I got the Jeep back from the dealer, but am tempted to open the TIPM cover and see if that little white fuse box is firmly seated.

IOD fuses have been around since the early '90s. Before that, we had large wires near the battery with bullet connectors that allowed them to be unplugged. You're right about their purpose. Unneeded accessories that are run by computers that have memory circuits that constantly draw standby current are disabled, but certain safety systems, like power mirrors, will still work only while the engine is running. They get powered up by the alternator and allow the delivery truck driver to operate things needed to do his job.

The TIPM is a computer module incorporated into the under-hood fuse box, and in my opinion, adds an unnecessary level of complexity where it is not needed. I left the dealership before those showed up, so I never worked with them there. I have worked on a few at my buddy's body shop. What I DO know about them I learned from the former head of Chrysler training for all of Wisconsin. She used to use my classroom as one of her three remote training sites, and I was allowed to sit in on those classes. (She was a REAL good instructor, and is where I learned some of my wondrous teaching skills).

Anyhow, getting back to the point, Chrysler was the first manufacturer to use a computer to run an engine, back in the mid '70s. There were only a few variations and the systems were real basic, compared to what we have today. When GM started using computers, there were quite a few variations, depending on the engine, year, and optional equipment. Chrysler had a different computer part number specific to each application. That made it impractical for a dealer's parts department to stock every one. Instead, they had to order them as they were needed. Fortunately their failure rate was extremely low. GM went a different route that made more sense. They only had a few computers that covered almost all applications, then they plugged in the "PROM", (programmable read-only memory), specific to the application, to give the computer its personality, so to speak. They had a very high computer failure rate in the late '80s to early 90s, but you could use almost any replacement then just transfer the PROM to it. No one had to stock a big bunch of different computers.

That has been taken to a new level now with downloading software into a new computer. GM, in my opinion, is the innovator at coming up with stuff that benefits them at the expense of their customers, and this was one of them. Unfortunately, everyone else seems to copy new ideas within a few years, and this is where your new TIPM is finally related to my wondrous story. The new TIPM will work on many years, engines, and models with a variety of optional equipment. The software has to be downloaded specific to the vehicle, and on some applications that can only be done once. GM did that so you can't buy a used computer from a salvage yard. You have to buy a new one from their dealers, and you have to pay them to install the software. That is one of their "customer-unfriendly" business practices.

I don't know if that one attempt applies to your new TIPM, but if it does, during the download process, the computer goes out and looks at the vehicle's circuitry and tries to talk with the other computers. If, for example, it doesn't find an Anti-Lock Brake Computer, it will know that option isn't there, and it won't include software for it in the download. To do so would cause it to set diagnostic fault codes later when it can't find things during the self-tests it runs. The point is, you need to have everything installed and connected, so the computer can detect everything and ask for the necessary software to be included in the download. That could be why they don't want to get the radio or interior lights working until the amp is installed. I should mention too, that starting with a few 2004 models, the industry changed over to the current "CAN-BUSS" computer system that standardizes a lot of stuff, and it adds a huge amount of complexity to the electrical system. What used to be a simple, reliable door switch, head light switch, cruise control switch, etc., are now a tiny computer modules. The manufacturers tells us that makes diagnosis much easier because we can read fault codes that tell us where to start looking, but those little computer-infested parts CAUSE more problems than they solve. Also, people like me can no longer buy the same testers the dealers have to buy, so I, as a mechanic and electrical expert, have to take my car to the dealer for many repairs that I should be able to do myself. That is the main reason I have resisted buying a newer car.