Dome lights quit working?

I've got a weird electrical issue that just popped up on my 1995 Tahoe 2 door - the two overhead dome lights stopped coming on when you open the doors or rear hatch.

The two courtesy lights down at the floor on each side of the vehicle still come on when you open the doors and hatch, but not the overhead lights. I can manually turn the overhead lights on at the switches on the light fixtures themselves, but not by turning up the switch on the headlight switch assembly. In fact, I push the button on the dome light itself, it will turn on, but if I roll the manual switch on the headlight switch assembly all the way up, the dome light will then turn off.

The headlight switch is fairly new; I replaced it not too long ago.

I'm not sure where to start troubleshooting the problem; seems strange to me.

Any ideas?

Casey

Sounds like the headlamp switch, or the BCM. New headlamp switches fail, and are a lot less expensive than the BCM.

Well, it's not the headlamp switch. I installed a brand new, Genuine GM switch, but there's no change. The overhead lights will only illuminate (very dimly), if the override button on the headlamp switch is depressed, same as before. If I turn on more than one overhead lamp, they get real dim, as in barely illuminated.

Does a 1995 model even have a BCM?

I guess it's time to dive into the wiring and see what's going on....

Casey

Dimming, then more dimming as the circuit load increases, suggests a connection or switch weakness. If it's only the one lamp, disassemble and clean it. Find out where it gets the ground (which may be switched, in a collapsible circuit), and give it some attention. If it's more than one lamp, the problem has to be at some point they have in common. A diagram would be very helpful.

1995 models probably don't have a BCM. Serial data was fairly simple on them, and I've never seen chassis/body codes on one. I had a 1995, and everything worked, so I had no reason to look for any modules. I did replace the HVAC control head, but that one was easy. It smoked then quit completely.

It's three lamp fixtures all together that quit working. The two overhead dome lights that come on with the door light switch, plus the dual overhead map lights. They were working just fine and then they weren't.

I'll have to start tracing the wiring down. I'm curious if it's a ground or positive issue.

Casey

Unless all three share the same ground, it can't be the ground.

I'm voting on ground issue Casey. Our Tahoes have some funky switches on the back door. I've had issues with these lights and lock functions associated with that back door as long as I've had it. Could be something going on there too. Seems weird, but that is what you called this issue in the beginning!
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I haven't had time to dig into this issue yet, but yesterday I just remembered that this rig has a feature that keeps the dome lights on for a short while after you close the door. That means there must be some sort of module somewhere that has a built-in timer. Perhaps that could have failed? Any idea where that bugger might be located?

Casey

If any 1995 GM models have a BCM, nobody is talking about it, and parts suppliers never heard of it, so that's out. If it has RKE (Remote Keyless Entry), it may have something to do with it. I did find a reference to the ILM (Interior Lamp Module), but it was for OBD II models, before the BCM was a thing. 2 possible locations for these modules, if you have one, is either in front of the glove box (likely on 1997+ models), or above and between the steering column and APP module (skinny pedal). Any module or connector that's bright yellow are for the SRS system, so steer clear of them, or pull the fuses first.

I was finally able to repair my dome light issue. I'm not entirely sure of the exact cause, but the problem was lack of 12V + to the light fixtures. Ground was present, but no 12V +. I had already run an aux. 12V + circuit for some accessories, so I simply tapped into that circuit. Now the lights function as normal once again, and work off the headlight switch as designed.

I assume there is a broken wire on the other end under the dash somewhere (probably due to me removing the dash for the heater core replacement this past winter). This was an easier fix than trying to trace down the other end of the circuit. It was super easy, barely an inconvenience.

Casey