I have a 2004 Chevy Blazer 4dr, 4wd, pwr locks/windows. I have been having a problem with the interior lights, they will not shut off. I have pulled the fuse for now.

Here are the things I have attempted to try to fix it:
-checked all door sensors and disconnected them
-disconnected latch sensors on front two doors
-checked relay box under dash on driver side, all wires connected, relays function
-there are two plugs on headlight switch, disconnected the larger one. The smaller one goes to the dome override
-replaced BCM (dealer install)

When all doors are closed the lights stay on normal for a few seconds, when the cycle ends and they should shut off they become slightly dimmer. If a door is opened or turned on using the dimmer switch they brighten up again. If the vehicle is running they seem to fluctuate in brightness a little (while the lights are dimmer) like there is a variance in voltage.

I had a friend connect it to a scan tool, it indicated that the front passenger door was open. I disconnected the door pin in the dash and later the latch sensor in the door without success.

The only modifications done to the vehicle electronically was the installation of a ham radio and xm radio. Ham radio electric lines are run through the firewall to a power connection in the relay/fuse box under the hood and grounded to the body. XM is plugged into cigarette lighter.

With the driver door open and pin depressed simulating a closed door, I replaced the fuse while working on it to check and they remained off, I hit the dome override and they turned on. I tested the door pin and it appeared that the lights were functioning normally. When I closed the door the lights remained on after the normal delay, although slightly dimmer... almost like closing the door rattled something.

I've searched the forum and read other threads with similar issues, and tried the advice given there without success.

I am at a loss as to what direction to take now. Any advice you can give would be greatly appreciated. My last resort is to take it back to the dealership for them to trouble shoot.

Thanks!

 

Sounds like your courtesy lamp relay may not be unlatching properly as it times out. I believe that the courtesy lamp relay is what controls the fading out of the interior lighting. I'd have to check my references at home to confirm which I would not be able to do until tomorrow.

 

Thanks for the info, I will pick one up and keep you posted.

Replacing the BCM has created other "problems". Apparently the Blazer has keyless entry. I was not aware of this when I bought it, but now every time I open the door with a key the alarm goes off. The dealer is working on a solution until my new key fob comes in.

Seems the gremlins are breeding!

 

Replaced the relay, still had the same problem.

I then removed the relay and the same problem persisted, the lights stay on only dimmer than normal (see original post).

Just so that I know that I am working in the right location I am in the dash on the driver's side near the brake release handle next to the fuse block. It would be infront of your left knee if you were sitting in the driver's seat.

So it appears that the lights are in the "off" position but they are still staying on.

I am running out of ideas, I studied the schematics a little more today and am at a loss...

Thanks again for any suggestions.

-Jim

 

Could it be a bad connection in the pin itself? Mine did that one day. I pilled the pin out of the side of the dash, took it apart and cleaned it. No more problems. My light was staying on intermittently. It was also coming on after arming the OEM "alarm", causing it to go off while I was in the store, Blockbuster, etc...

 

Disconnected all the pins (including rear hatch) and the latch sensors on the front doors.

The alarm problem is new and I believe totally unrelated to the light problem.

 

Here is the description of the courtesy/illuminated entry lamps for your truck:
And even with the switches disconnected, you could still have a wire grounded out somewhere that is telling the BCM that a door is open.

 

UPDATE

Finally got back to this project and here is what additional things I have done...
-removed headlight assembly, inspected and replaced
-checked all wires coming from door pins
-checked relays near brake pedal

Before I get scolded for doing this with power to them, I took the risk because the lights were triggered and I needed to diagnose removing one thing at a time without shutting the lights off...

Here is something interesting that happened that may help with a suggestion. I put the fuse back in and it worked fine for a day, then the problem returned. Did the above and it went away, and then returned immediately.

I could hear the relays trigger and release, so I thought one might be sticking. I removed the relays one at a time, and then all of them and the lights stayed on, then removed the plugs from the BCM with the same result.

It's important to note that even though the lights stayed on they were noticeably dimmer than when they are on with the relay triggered.

So here is where I sit, all the doors are closed and the pins are functioning normally. All of the relays were removed, BCM unplugged, AND the headlight switch is disconnected. the lights remain on, although dimmer then if they were supposed to be on.

What do I try next?

Thx for the help.

Also, if you would be willing to talk this out a bit on the phone I can give you my number or call you and save the long distance with the understanding that it won't be a repetitive thing. Email can work too.

 

Best to keep it all on the forums where it can benefit all.

After all of this, it definitely sounds like you have a short to ground in the wiring. The short could be anywhere between the courtesy lamp relay and the lamps themselves.

 

Forgive me for not being able to wrap my mind around this, but...

This is how I understand it... Power goes to the relay box that acts as a "lightswitch" when the light switch is ON power passes through to the dome/courtesy lights. The light bulbs are between the power and the ground.

For clarification, I understand all the S### to be switches or are they splices. If they are splices I will need those explained.

I have the overhead console w/o sunroof.

I'm really gonna owe you pizza and brew after this.