Battery light always stuck on and interior lights only work intermittently

Hi,

When you checked the alternator output with the engine running, was it producing approximately 14v? If so, then the first thing I'm suggesting is to check the ground for the instrument cluster. This could be causing both problems you mentioned.

I attached the wiring schematic below for the charging system and highlighted the ground location. Check that and let me know what you find.

Note: The ground will be located on the right side of the steering column and secured to the body. It will be a black wire with a white tracer.

Let me know what you find or if you have other questions.

Take care,

Joe

See pics below. Note: I had to cut the schematic in half to make it readable for you. I did overlap the two so you can follow from one to the next.

Hi,

Here is my theory. I suspect the problem is in the instrument panel/cluster. If the red wire with a white tracer to the IPC is getting power, the ground is good, and there are no loose wires on the battery or alternator, that is my first suspect.

Since you indicated the lights behind the speedo don't always work. To me, it sounds like there is a short in the cluster.

To determine if there is an issue in the IPC, body control module, engine control module, or the can-bus system, the vehicle should have the can-bus scanned for codes. CAN stands for controller area network. Basically, all computers/modules are tied together via a few wires. This scan type will identify codes regardless of the module storing them.

Here is a quick video showing how it's done:

https://youtu.be/u-4syLc-ifQ

This would be what I would suggest next. Otherwise, it will become a guessing game.

Let me know your thoughts. Also, if I don't hear from you for a couple of days, have a Happy Thanksgiving.

Take care,

Joe