NEED HELP Brake light issue...HELP!!

[Rhondaf]

I have a 2003 chevy trailblazer with the driver side rear brake light not working, I have checked fuses (they are good), changed the bulb, the light bar, and the break switch under the pedal. I'm lost.
it is missing the panel at the top that should have the third break light, but that has been gone since I got it and the break light worked fine for about a year. I've taken it to a shop twice and both times they said there wasn't anything wrong with the break light and both times it came out of the shop with the same issue (same shop both times). Does anyone have any other ideas? Please help me!!

 

[TJBaker57]

I've taken it to a shop twice and both times they said there wasn't anything wrong with the break light and both times it came out of the shop with the same issue (same shop both times).

This seems sort of odd. When you picked it up at the shop did you try it right there? Is it working sometimes, like at the shop, and then not working later?

 

[Mooseman]

Hi and welcome.

That would be brake light. Just a pet peeve here

Quick question, does your turn signal and parking light also work on that side? If not, I would suspect the loss of the ground connection as that affects all the lights on that same side.

The shop you took it to isn't worth their salt if they can't even figure out a simple electrical issue like this. Just a matter of finding the break in the power flow.

Look at the attached schematic.Then follow the flow from Fuse 34 and, with either a multi-meter or a test light, start tracing power from the bulb going back until you find power. Start with checking if ground is there against a known good power point (i.e. the battery +), then, with someone or something holding the brake pedal down, check for power from the bulb socket going back to the fuse. Check in the connector. It is a single light blue wire going from the connector to the fuse block under the rear seat with no other connector in between. Pull and tug on the wires as they sometimes corrode and break inside the insulation and socket.





The schematic shows two light blue wires at the left taillight socket. Turn on the left turn signal to eliminate that one.

If this is beyond your abilities, I would take it to another reputable shop. As you can see, power should be going from fuse 34 to the socket. Very simple issue that any good shop should be able to figure out in minutes.

 

[aaserv]

There are 2 lt. blue wires going to the board. Find the 1 to the brake socket. There is only 1 ground so likely there is a short in the Lt.blue voltage wire. If you dont have 12v to the blue when pedal is depressed then there must be a short somewhere if the shop got it to come on. I wouldnt discount the possibility you can have 12v to the new socket holder and it still doesnt work....New doesnt always mean good/working . But more likely is a broken wire where it exits the body and goes to the light. Here is a video on cking voltage to the board. You can see the rubber grommet in the background where the wires exit the body, after verifying you dont have 12v to the board I would pry loose that grommet and ck that area next for a broken/corroded wire.

 

[Rhondaf]

I don't believe the shop even looked at it. It was in there for other reasons as well as the brake light both times. Both the tail light and turn signal work on that side. We have tested the bar and it has no power, the old and the new as well.

Hi and welcome.

That would be brake light. Just a pet peeve here

Quick question, does your turn signal and parking light also work on that side? If not, I would suspect the loss of the ground connection as that affects all the lights on that same side.

The shop you took it to isn't worth their salt if they can't even figure out a simple electrical issue like this. Just a matter of finding the break in the power flow.

Look at the attached schematic.Then follow the flow from Fuse 34 and, with either a multi-meter or a test light, start tracing power from the bulb going back until you find power. Start with checking if ground is there against a known good power point (i.e. the battery +), then, with someone or something holding the brake pedal down, check for power from the bulb socket going back to the fuse. Check in the connector. It is a single light blue wire going from the connector to the fuse block under the rear seat with no other connector in between. Pull and tug on the wires as they sometimes corrode and break inside the insulation and socket.


View attachment 100032


The schematic shows two light blue wires at the left taillight socket. Turn on the left turn signal to eliminate that one.

If this is beyond your abilities, I would take it to another reputable shop. As you can see, power should be going from fuse 34 to the socket. Very simple issue that any good shop should be able to figure out in minutes.

I don't believe the shop even looked at it. It was in there for other reasons as well as the brake light both times. Both the tail light and turn signal work on that side. We have tested the bar and it has no power, the old and the new as well. Thanks for the information. I will trace the wires and see what I find.

 

[linneje]

I am going completely from memory here, but I seem to recall having the same problem but with my travel trailer brake light on one side. Perhaps it was also the vehicle brake light as well, but I can't remember. The problem was with a module or relay under the dash below the steering wheel. I can't remember the module, but I did it myself and it wasn't difficult. Fixed the problem.

 

[linneje]

Flasher module, I believe. GM part number 15231201

I think that is what I changed out, and the problem was fixed and never returned. But it was my trailer brake light, and I can't remember if my vehicle brake light was involved as well.

 

[Mooseman]

The brake and flashers lights are separate on the vehicle whereas for the trailer, they are combined. The module is not in play for the vehicle's brake lights.

 

[Reprise]

There's another thing to check, and that's the board ('tail lamp module') that the bulb plugs into. They can overheat and burn out (you'll easily see it if that's the case, as you'll often see the socket in question look like it melted (because it did)), along with brown discoloration on the white board / module. That means a new board gets installed, which involves cutting & splicing wiring back together, IIRC.

If you find this to be the case, then the shop likely didn't look at the bulb / board, or they'd have easily found it.

Get a small tube of dielectric grease (any auto parts store should have it; some grocery stores do, too, if they have an automotive section.) Place a little on the bulb sockets in the tail lamp assembly. That can help with the bulbs burning out in the future (and a small tube should only cost about $5 or so -- cheap preventative insurance).