battery indicator light

Yes, it could be the alternator or a wiring problem. Here is a how to for checking it. Do this and let me know what you find:

https://www.2carpros.com/how_to/how_to_test_alternator.htm

If the unit is bad this guide will walk you through the repair.

https://www.2carpros.com/articles/how-to-replace-an-alternator

Please run down these guides and report back.

had to replace the alternator cost me $134.00 I love this site.

My battery light keeps coming on the alternator and battery are good.

How was the charging system tested, and what were the results? This problem is acting up intermittently. Was the testing done while the problem was occurring?

Yes could not find anything out. my harness that plug's into the back of the alternator only has one wire do not know why.

Yes couldn't find anything out my harness that plug's into the back of the alternator only has one wire don't know why

It was tested with some type of battery charger and a electric tester by a mechanica I know.

There's a lot more involved with this type of problem. Most simple testers only check that the battery voltage is between 13.75 and 14.75 volts with the engine running. You can do that yourself with an inexpensive digital voltmeter. If that voltage is okay, that only means it is okay to perform the rest of the tests, but you need a professional load tester for that. Specifically, we need to know "full-load output current" and "ripple voltage".

All AC generators have at lest six diodes, and if one fails, all you'll be able to get is exactly one third of the rated output current. 30 amps from the common 90-amp generator is not enough to run the entire electrical system under all conditions. The voltage regulator will detect that missing one third of the output and turn on the "Battery" warning light in response.

If it is necessary to replace the generator, also look at the age of the battery. Due to the design, these generators develop a lot of harmful voltage spikes that can damage those diodes, and the internal voltage regulator, and they can interfere with computer sensor signals. The battery is the key component in damping and absorbing those spikes, but as they age and the lead flakes off the plates, they lose their ability to do that. It is common to go through four to six replacement generators in the life of the vehicle. To reduce the high number of repeat failures, always replace the battery at the same time, unless it is less than about two years old. If it tests good, it can still be used in an '86 or older GM car with the older generator design.

Thanks will try

The battery light will come on and will not shift on take off. the odometer light flashes then it runs fine for awhile but, stalls when the lights are turned on.

Sounds like your alternator is not always charging have you had your alternator tested yet?

It's new and putting out14.2volts

It's new putting out 14.2 volts

OK when it acts up are you watching the charging voltage at the battery?I have seen bad ecms cause random charging issues.Had a 2004 Chevy cavalier do that and it was a bad ecm because it controls the alternator charging.

battery light goes on rev engine and goes away ......but still no charge .... volts are 11.7 at the alternator or battery terminal
also how hard is to replace it , they mechanics ask my wife for over 450 parts and labor, please help

I can't speak to the difficulty, but starting in '87 with this design, GM generators have an extremely high failure rate. They develop huge voltage spikes that can destroy the internal diodes, voltage regulator, and interfere with computer sensor signals. To reduce the number of repeat failures, replace the battery at the same time unless it is less than about two years old. As they age and the lead flakes off the plates, they lose their ability to dampen and absorb those spikes.

You're right about the charging voltage. When it's working properly, you'll find between 13.75 and 14.75 volts with the engine running.

thanks you for the respond ,.......but my second question was the most important of the two.....how hard is to replace the alternator ......can i do it or i need to take it to mechanic one again thanks ed

GM never designed a vehicle with an eye toward service. Their concern is how it can go together the fastest on the assembly line. Also, there is no rhyme or reason as to where they mount things. The generator can be in one location in one vehicle, and a totally different location on the same size engine in a different vehicle.

I looked up the instructions for yours and found there's a lot of variables that I and probably you can't answer. You're going to have to look for yourself to see if you want to attempt this job. For the choices I selected, there are 16 steps in the list of instructions that include removing engine mounts to roll the engine forward to access some bolts, remove the drive belt tensioner, remove the generator's bracket, remove the power steering pump with a warning to not disconnect the hoses, and other steps.

There's also a tip posted that suggests lowering the engine cradle with the engine on it to make generator removal easier. If you want to try that, don't start until I explain what can happen to handling and steering response, and how to avoid those miserable problems.

I wasn't able to copy and paste the instructions. Your best bet is to get a copy of the manufacturer's service manual, then read through the steps with the line drawings to see if you want to attempt this job.

Hello, about last month my truck slowly started with idle problems it would hold an idle at about 3 rpms, so took it to mechanic and did obd. too many codes came up so we tried changing by codes. finally replaced main computer. mass flow sensor. tp sensor ect... after changing main computer, i suddenly now have a battery light that wont go off and i failed inspection for emissions not ready. i did another obd after replacing all those parts and i keep getting these codes. Po641 (5) volt reference 1 circuit, po122 tp or app sensor 1 circuit short or low, po453 evap pressure sensor signal high, p1122 tp circuit low voltage, p1819 internal mode no start, wrong range, help please i am unemployed and have 2 small children i ve already put 1000 of parts i probably did not need to change. i also changed alternator.

If the battery light comes on occasionally during acceleration or uphill driving, go to any GM dealership and ask them to look up a TSB on a Rendezvous "battery light on" issue. It takes one hour labor to reprogram the computer.