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Cruise Control, all 3 brake lights out

15K views 30 replies 10 participants last post by  DocHaley 
#1 ·
I am trying to search the forums for answers to this. I apologize if it's been answered.

Can someone get me started troubleshooting this? I realize these can be separate issues, but I noticed someone else on the board had the same situation. (Both Cruise Control, and ALL 3 brake lights out.)

I have a 2002 Trailblazer. I called autozone and they tried to tell me that there are no fuses for the brake lights on a 2002 Trailblazer, and wanted to sell me the pedal switch.
 
#3 ·
No, because 1. I don't know how to test a fuse. 2. I don't know which one's to test. 3. I was told by Autozone, that the fuses are irrelevant.

I am hoping someone who knows what they are doing can steer me straight and say something like - Replace fuse X and Y and it should work.
 
#5 ·
Some Autozone staff seem to be in a competition to see who can be the dumbest neanderthal in the world so they can get picked for next season's Big Brother. I swear.

The cruise control switch is also fed power from the HVAC1 fuse #39 in the rear fuse block, but a failure of that wouldn't take out the brake lights. I bet Ray has it nailed. Some things he nails first, and I just stand by and cheer him on. :eek: :woot: :thumbsup:
 
#7 · (Edited)
Okay- I actually went and tried this right away.

I have my truck parked in the garage so it is easy to see the reflection of the brake lights off the door.

I checked fuse #12. Yep you were right. It's fried. (I'm no tech, so forgive the simplicity of my language here.) The 'silver' band inside the fuse was broken.

I replaced the fuse with the extra '25' on the side. I pressed the brake pedal...

The brake lights lit up for about 1 second, then went out. Checked the 'new' fuse. It was blown. (Silver band melted away)

So something is blowing the fuse out when I press the brake pedal.

Now What????
 
#8 ·
Sounds like a nice little short somewhere in the brake light circuit. My first guess, knowing that they had some issues, would be the circuit board attached to the tail light assembly. You will need to get a couple of fuses to test it. I think you can unplug one of the tail lights completely and press the brake pedal. If it blows the fuse, plug that one back in and unplug the other side and try it again. If it still blows, at least you will know its not either of the brake light assemblies...... but I would bet a dollar that it is one of them.:cool:
 
#13 ·
The circuit boards have an aftermarket supplier now, so they're not a GM only part. That (like when Southwest Airlines comes to a city near you) always lowers prices. I think they're even as low as $20.

Looked it up at Rockauto for you - even better than I thought. DORMAN Part # 70006 - $12.04. So a fair price at your local parts store if you need one would be under $20. Ghoster can pay extra for his non-trailvoy parts. :dielaugh: :laugh: :raspberry



No need to buy an entire tail light assembly for big $$$ if it's an electrical problem.

Your problem could be an abraded wire somewhere hidden from view inside the fender, though. I'd get a flashlight and go back in there. If a fuse blows right away, that's proof of a real short, not just a corroded lamp socket or something like that. When you removed the light assemblies to disconnect the connectors, that moved the wire harnesses back inside the vehicle where you couldn't see. That's where I'd guess you have a wire with nicked insulation. It may last a long time before it jiggles and shorts out again, or it may never do it. But for my own curiosity, I'd take them off one more time and look if possible.

Fuses are very seldom "weak" in that way, but it's a good guess.
 
#15 ·
Start by inspecting them at the rubber grommet behind the tail light. They disappear into the fender, but you can remove interior plastic panels to look for the wiring harness inside. A complete how-to article with pictures of how to remove interior plastic panels is beyond the scope of this thread. Unless some other volunteer has more time than I. ;)
 
#18 ·
I'd be a little hesitant about jumping to the circuit boards first, I'd suspect a short in the wiring, or at the switch.

Reason: the fuse that's blowing is 25Amp. The brake lights run through a 2nd fuse (#34 in rear panel) and it's only 15A.

If a circuit board was shorting, the 15A should pop first (I know sometimes the opposite is true, but usually, they would both go).

And, jaywdetroit, fuses can be old and sometimes pop because they are brittle, but you lost 2 and 25A plus is a big draw. You have a short somewhere, it's just hiding for awhile
 
#29 · (Edited)
Same problem but a bit different

Can you guys expand this problem?
My 2004 TB has no blown fuses. I did just replace the lighter fuse since I was trying to use a test module and it was fed from the cig lighter service.
I checked my fuses, all are good.
I did replace my left rear tail light assembly a few weeks ago but I'd be shocked to think it would go bad this soon? Or is it not unusual? Piece of crap is a piece of crap?
What do you think I can do to figure it out?
Really thank you folks for your smarts, it helps out dummies like me.

Forgot to add in: This all started because my cruise control just stopped working.

Doc
 
#31 · (Edited)
Done so far


Last week or two replaced drivers side rear tail light assembly. Some fool bumped it and cracked it. I just decided to replace it, just because.
Today the cruise would not work. No back brake lights (all 3 are out).
Put new bulbs in and tested every socket. All bulbs are good.
Checked out fuses because I had to use a tester and found out the cig lighter fuse powered the test plug under the steering wheel. Replaced it and got the code (gas cap issue. been done and everything was good to go)
Last option seems to be a brake switch? Is it really an issue? Is it really a part that fails? A brake pedal light switch?
Doc
 
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