Battery light on?

Hello,

It sounds like you have an alternator that needs to be replaced but to be sure here is a guide to confirm the issue with a guide to help walk you through the alternator replacement if needed

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

and

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

Please run down these guides and diagrams and report back.

Hi,

Is the alternator charging the battery? Do me a favor. Try this simple test to confirm charging. All you need is a multi meter or volt meter.

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

With the engine off, you should be right around 12v at the battery. With it running it should be near 14v. If it is charging, then there are a few things to check. I attached two pics below of the charging system. In the first pic, I highlighted a fuse to check and also a ground.

Do that first and let me know what you find.

Joe

Are you able to check for power to the pink wire going to the instrument cluster. We could have a bad connection or damaged wire. I'm asking this because if the fuse is good, the next think to check is if power is making it to the IPC.

Let me know.
Joe

Okay, can you check for ground to the black wire. Basically check for continuity to ground. If there is ground, I suspect something has failed in the cluster.

My thought is either corrosion on the battery cables, especially the negative, check for voltage drop on the both cables. Shut off the truck. Measure battery voltage, then measure the negative cable at the block and + battery post, if not the same as battery voltage replace the cable, do the same on positive cable but touch _ post, readings should be battery voltage. If OK re check connection to alternator, and check small ground spur wire to the fender if you have one. Also when you say no codes, did you scan it with a tool capable of reading B and U codes? Or with a generic tool for P codes? B and U codes cant be read with generic tools and do not set the service engine light. This truck has a generator battery control module that monitors the charging system. And the first step is ALWAYS to scan.

It is the black/white one. Disconnect the battery when checking for continuity. Power is showing negative, so somehow the battery polarity is getting reversed. It is likely because the battery is connected.

Hi,

I assume you are talking about the diode test when you got .033 volts AC at 1200 RPM?

If that is the case, then yes a diode has failed and you need to replace the alternator. This will cause your battery to fail and a new battery on a bad alternator would last about a week depending on the load and use.

The battery light simply means there is not sufficient voltage present so it is normally the battery or alternator so I think you have enough to feel confident that the alternator will fix this.

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

Let me know if you have questions. Thanks

The charging system has to be tested while the light is on and the problem is occurring, otherwise, of course it will test okay. GM has WAY more trouble with their generators than anyone else, but intermittent problems are not common. Usually they just fail. When they do, to prevent a lot of repeat problems, replace the battery at the same time unless it is less than about two years old.

The battery light usually indicates a problem with the charging system. You need to have your battery and alternator tested. Most auto part stores such as AutoZone or Advance Auto Parts will test them for free, on or off of the vehicle.

If both test good then check the battery terminals and cables for corrosion and ensure they are tightened properly.

This guide can help

https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked

Thanks for using 2carpros.com!