Alternator charging light turns on?

Tiny
JOSEPH19832
  • MEMBER
  • 2004 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
I have checked the alternator battery all the wiring and the grounds in the engine but the battery light in the cab turns on and off along with the message center telling me the battery is not charging turning on and off.
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Monday, September 23rd, 2019 AT 1:31 PM

35 Replies

Tiny
ASEMASTER6371
  • EXPERT
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
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Monday, September 23rd, 2019 AT 3:50 PM
Tiny
JOSEPH19832
  • MEMBER
Their is 14.6 at the battery and 14.7 at the alternator. Also the battery is holding a 12.5-12.6v charge.
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Wednesday, September 25th, 2019 AT 3:16 PM
Tiny
KEN
  • ADMIN
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.
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Wednesday, September 25th, 2019 AT 3:22 PM
Tiny
ROUNDMAN711
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 27,000 MILES
In my message center on the dash the red battery icon keeps coming on and off. I have duel batteries(camper package). Even when it is lit the volt meter still reads over 14 volts. The battery has not gone dead. Both batteries are original. Someone told me it might be a diode in my alternator.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
CB60
  • MEMBER
I have the same problem with my 2002 silverado. Did you ever get it fix and if so can you tell me what td do.
Thanks
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
2CEXPT
  • EXPERT
TO: CB60

Sounds like you need to have the computer controlled of the alternator's field generation circuit -checked
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
CB60
  • MEMBER
I put on a " new" alternator and belt today and the light went out. :) Hope this helps you.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
ANGEL LONG
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 250,000 MILES
The truck will start. It'll run. For a while. The AMP meter slowly drains. Eventually it starts to backfire and shut off. The speedometer is no longer working and neither is the radio. Also the windows are very slow to roll up/down. I looked at the fuse panel inside and the RAP relay is missing. I've had the battery checked. It's good. I had the alternator checked and I was told it was bad. My friend and I purchased another used alternator and changed them out. It's still running the same. Starts. Runs. Shuts off. I figure either the used alternator is bad, or there's something else going on. I wanted to get an outside opinion before purchasing a brand new alternator. All thoughts on the matter are welcome.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
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
____________________________________

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
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
ANGEL LONG
  • MEMBER
Okay, here's an update: I took the alternator off the truck and had it tested separate. Tests say it's good. I took a peek in the fuse box under the hood and low and behold there's two wires running directly from the box to the brake pedal. We're thinking it has been rigged by the previous owner to work the trailer lights. Thoughts? Also the remote jumper terminal is melted and corroded. Definitely needs replacing.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
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
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
ANGEL LONG
  • MEMBER
The wires go to the brake switch. The last pic is of the fuse block on the inside.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
MIKE0555
  • MEMBER
  • 2002 CHEVROLET SILVERADO
Electrical problem
2002 Chevy Silverado V8 Four Wheel Drive Manual

battery light is flashing, battery is charging, alternator putting out 13-14 volts, battery 12 volts wihen not running
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
2CEXPT
  • EXPERT
Get the computer controlled of the alternator field generation duty cycle signal circuit checked out and also check battery and alternator connections-
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
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
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
ANGEL LONG
  • MEMBER
We replaced the jumper. It's getting connection a lot better, but it still doesn't want to start after running a while. None of the gauges inside are working now. The wires do work the brake lights. Do you think that's wearing the battery down? Side question: as you can see in the third pic I posted, the RAP relay is missing, do you think that has anything to do with the problem? Also, my mechanic friend says the clutch fan needs replacing, would that run the battery down?
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
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
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
ANGEL LONG
  • MEMBER
Sorry I've been MIA. I've been doing research and today I got a friend to let me hook up their scanner. It popped up 4 error codes. 2 of them were the Knock sensors. 1 was an Evaporative Emissions sensor and the last was a Random Misfire error code. We're going to test the vacuum hose for leaks and of course I'm going to purchase and install the Knock sensors ASAP. However there are a few other things that are troubling me about the truck. 1. None of those codes explain the brake light problem we're having. As you know, the previous owner/my dealership rigged up a bypass to the brake switch by running two wires directly into the fuse box. Well we purchased another brake switch, installed it, rewired the brake switch from the fuse box to the appropriate wiring and nothing. We still have no brake lights. I'm not sure what the problem could be. Do you have any ideas?
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
MYSOFTAIL98
  • MEMBER
  • 2002 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 91,000 MILES
I have a 2002 Silverado Z71 5.3L with 91K miles. My battery light comes on for a few seconds and then off again while driving. Also sometimes the votage jumps back and forth from 14.6 to 13.4 at idle. I have replaced the alternator with a new delco 130 amp. I also change the belt at the same time. The battery is about 7 months old and I have tested it just to make sure its good. Lastly I had a new PCM installed from the dealer. Where should I look next? Thanks for any help.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)
Tiny
ZACKMAN
  • MEMBER
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.
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Thursday, September 3rd, 2020 AT 6:25 PM (Merged)

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