1999 Mercury Marquis Electrical Problem

have your charging system checked and make sure battery terminal ends are clean. auto parts do this for free

I took it to my local shop and they checked the charging system. They told me that the charging system checked out good. I used a baking soda/water mix to clean the battery terminals & cables. After this I am still having the same problem. Additionally, I have noticed that when the power goes out and I turn on my lights the clock also goes out but when I turn the lights off the clock immediately comes back on.

check tosee if your battery to body ground is hooked up or broken this may be the cause of it. then check the tings I've pointed out in pic for the fusible links seeif only one or two strands are holding them together. they shold have have same voltage on both sides.

Put the new battery in on Tuesday and yesterday it was dead. I checked the grounds first and everything was good but just to make sure I unscrewed and cleaned both of them. Then I checked the thinks that you mentioned and everything checked out fine. I hooked the battery to my bench charger and once it was finished I plugged it back into the car. I checked the volts and when the car is off the battery was reading 12.90 volts at the terminal. I also checked the volts using the positive terminal and both grounds, the negative terminal and each fuse in the power dist. box, and the negative terminal to the positive cable on the alternator. All came back between 12.8 - 12.9.

I went to start the car and it just clicked so I checked the battery again and it had dropped to under 8 volts. Once I jumped the car the battery was reading 16 volts so I checked all the same things and all came back between 15.9 and 16.

I left the car run for a little over an hour then turned it off. Went back out this morning and the battery is dead again.

either this battery is bad or won't hold a charge or something is draining the battery overnite. go to how to repair, battery item 9 it will tell you how to check it. the battery may ffail a load test which auto parts can check as well as tire stores/repair shops. You might end up taking this to arepair shop to get this fixed as it's hard for us to diagnose a problem similar to yours.

I had a brand new battery put in on Tuesday. Is it possible that the alternator is draining my battery? If the motor is not grounded properly and the alternator is grounded using the bolts to the motor, could that cause the alternator to pull power from the battery when the car is off?

I don't have an issue replacing the alternator, I just hate to replace parts that aren't bad. It's getting to the point that the value of the car is less than the repairs I have put into it.

if an alternator is bad it is usually the diode or diode bridge is bad an dletting poer go back through it when it shouldn't .you have to do a draw test on this which I sent how to get to it on site here. then disconnect the alternator large wire. if light goes out alternator is in need of replacing. what it means even though it charges it draws the battery down when ever not running. Bu tit cold be something else doing the draw as well a test light or volt meter should go out when ever you find the draw. lHowever newere cars will have a lsight draw to them all the time, not enough to discharge a battery overnite but a slight draw like in millivolts.

Draw test came back with no light. I noticed now that with the car off the battery will read around 12.6 but as soon as I start the car the voltage jumps to almost 17 and will slowly get to almost 18. Could the internal lights and heater by shutting off as a reaction to the over voltage?

voltage should be 15.3 max unless your meter is off.It might climb that high at first but shold level off at 15.3 at the most with lights an dheater working. I really suggest that you take this to a pro to see what they can figure out as some of these are kind of hard for us to figure a problem out like this without actually seeing what is going on ourselves...