Alternator charging light turns on?

Good evening.

Can you check the voltage at the battery with the engine running?

https://www.2carpros.com/articles/how-to-check-a-car-alternator

Roy

If I can step in here. it sounds like the have a bad PCM that is what controls the alternator. To be sure here is a guide to check the wiring with the alternator wiring diagrams so you can see how the system works and the PCM replacement instructions as well:

https://www.2carpros.com/articles/how-to-check-wiring

Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.

TO: CB60

Sounds like you need to have the computer controlled of the alternator's field generation circuit -checked

Hi,

If you see the alternator gauge dropping, chances are the alternator is the problem. Do me a favor. I want you to check the alternator output. It is very easy to do. All you need is a volt meter or a multi meter. Here is a link that explains how it is done:

https://www.2carpros.com/articles/how-to-check-a-car-alternator

I don't know if you need it, but here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

If you find the alternator isn't producing and needs replaced, here is a link that shows in general how it is done:

https://www.2carpros.com/articles/how-to-replace-an-alternator
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Here are the directions specific to your vehicle for replacement. The attached pics correlate with the directions.

2002 Chevy Truck K 1500 Truck 4WD V8-5.3L VIN T
Generator Replacement
Vehicle Starting and Charging Charging System Alternator Service and Repair Procedures Generator Replacement
GENERATOR REPLACEMENT
REMOVAL PROCEDURE

CAUTION: Refer to Battery Disconnect Caution in Service Precautions.

pic 1

1. Disconnect the negative battery cable.
2. Remove the accessory drive belt.
3. If necessary, remove the engine sight shield.

pic 2

4. Disconnect the generator electrical connector (3).

pic 3

5. Remove the generator cable from the generator, perform the following:
5.1.Slide the boot down revealing the terminal stud.
5.2.Remove the generator cable nut from the terminal stud.
5.3.Remove the generator cable.

pic 4

6. Remove the generator bolts.
7. Remove the generator.

INSTALLATION PROCEDURE

pic 5

1. Install the generator.

NOTE: Refer to Fastener Notice in Service Precautions.

2. Install the generator bolts.

Tighten
Tighten the generator bolts to 50 N.m (37 lb ft).

pic 6

3. Install the generator cable to the generator, perform the following:
3.1.Install the generator cable.
3.2.Install the generator cable nut to the terminal stud.

Tighten
Tighten the generator cable nut to 9 N.m (80 lb in).

3.3.Slide the boot over the terminal stud.

pic 7

4. Connect the generator electrical connector (3).
5. If necessary, install the engine sight shield.
6. Install the accessory drive belt.

pic 8

7. Connect the negative battery cable.

_________________________________________

Let me know the results you get when checking the alternator. Also, if you have other questions, let me know.

Take care,
joe

Interesting about the wires. Are the connected to the brake pedal switch? Is it possible for you to upload a pic of what you found? I want to see how they are in the box. If possible, attach a pic of the remote jumper cable you mentioned.

Let me know.
Joe

Get the computer controlled of the alternator field generation duty cycle signal circuit checked out and also check battery and alternator connections-

Since the jumper wires they attached are pushed in, disconnect them from power and see if the brake lights still work. If they do, I suspect those were for an electrical brake controller.

Also, pic 1 shows a lot of corrosion. Disconnect the battery, remove the nut (pic 1) and clean everything to confirm a good connection.

Let me know what you find.

Joe

As far as the RAP, that is energized until you have the key removed and open the door. If the door isn't opened, it will power certain accessories until a predetermined amount of time passes. Since there isn't one, I have no idea if the prior owner is powering some things all the time. The RAP continues power to things such as the power windows, radio, Onstar and so on. Do any of those things remain powered after the key is in the off position and prior to opening any doors? Note there are two RAP relays. See pics 1 and 2 for locations.

As far as the loss of instrument panel gauges, did you check fuses where you were working? Also, have you ever been able to identify if spark or fuel is missing when it refuses to start?

Joe

Check your belt tensioner. Over time, the spring in the tensioner assembly gets weak/damaged and the belt gets loose and not properly tensioned. This will cause the light to turn on.

You may also wish to bring the vehicle to a parts store and have them check the entire electrical system, not just battery, but starter and alternator.