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1996 GMC Jimmy brake lights

Tiny
KEV3W2H
  • MEMBER
  • 1996 GMC JIMMY
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 130,000 MILES
The brake lights stopped working on my blazer. The middle break light works when the break is depressed but not the bottom lights.
Could this be a ground and if so where would I look for the bad ground? I am inclined to believe that the switch on the break pedal works (being that the middle light is working. Is it also possible that there is a seperate fuse for the break lights /middle light>?
after a little proding I realized that there are two sets of lights for the breaks, turn signals, tail, and hazzards, when I turn the lights on and the turn signals, two of the filaments for the lights and two for the turn signals come on.
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Saturday, December 27th, 2008 AT 1:11 PM

9 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Replace the turn/hazard switch your power goes thru there before it gets to the bottom brake lights.
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Saturday, December 27th, 2008 AT 7:38 PM
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
Hello
Thanks for the donation.

I believe the high mount stop lamp is seperate from the rear stop lamps. Check the relay for power located at center rear of engine compartment. You may also want to start with replacing bulbs. Your bulbs are double filament which means that they actually have two lights in it.

Post results and I will follow up.

Thanks for using 2carpros. Com!
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Saturday, December 27th, 2008 AT 7:42 PM
Tiny
KEV3W2H
  • MEMBER
  • 8 POSTS
I have checked for the relays and the only ones on the engine are the air conditioning relays( I am still looking), The bulbs are all lighting. Ex. There are two filaments on each bulb, one is above the other, both upper filaments work with the lights on, and when the turn signals are activated, the lower filaments come on. I checked another blazer (of another year) and found that the turn signal overides the breaks.
As for the hazzard switch, does this send power to the brake pedal switch? Is the break pedal switch a simple on/off switch or does it send different amounts of current out. It seems like some current is going out of the break switch in order to run the middle light, maybe not enough power to run the other lights.
Sorry about all the questions, just trying to understand how all of this works.
(hazzard switch )>(break switch)=lights ?
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Sunday, December 28th, 2008 AT 7:41 AM
Tiny
BLUELIGHTNIN6
  • MECHANIC
  • 16,542 POSTS
No problem at all. That is what we are here for. :)

If all filaments in bulbs are lighting then my suggestion would have to be to replace the brake light switch. You CAN adjust them if you feel this will help.

Brake light switches are mounted on brake pedal arm. When brake pedal is not in use, it depresses the switch's plunger [holding the switch OPEN] shutting off the brake lights. When the pedal is depressed it allows the switch plunger to extend, closing the switch and allowing electrical current to the circuit and the brake lights illuminate.

Switch is mounted by screwing a threaded nipple on the switch into a threaded hole in a mounting bracket. This switch is adjusted by screwing the switch further out or in.

For wire troubleshotting you should check around the trailer connector for a short. Also under the bumper should be a harness that splits off the taillights. Take a circuit tester and check for shorts here as well.

The high mount (third) brake light is not wired through this switch but the two brake lights are. The switch also cancels the brakes for turn signals and hazard lights and it will wear out eventually.

Hope this helps.
Thanks for using 2carpros. Com!
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Sunday, December 28th, 2008 AT 11:06 AM
Tiny
RASMATAZ
  • MECHANIC
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Below is the exterior lights EWD -unable to read it give me your email addy.


https://www.2carpros.com/forum/automotive_pictures/12900_turn_and_hazard_switch_jimmy_1.jpg

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Sunday, December 28th, 2008 AT 11:30 AM
Tiny
KEV3W2H
  • MEMBER
  • 8 POSTS
Kev3w2h@yahoo. Com
I have the haynes manual.
Your schematic looks a little different but like you said I cant read it.
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Sunday, December 28th, 2008 AT 3:32 PM
Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Its on its way-let me know what's going on
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Sunday, December 28th, 2008 AT 4:26 PM
Tiny
KEV3W2H
  • MEMBER
  • 8 POSTS
Thankyou for the schematic. Tomarrow I plan to try changing the hazzard switch. I took the break switch off and found that there is not any adjustment to it. I have power to the hazzard switch but cannot tell if there is power leaving it.
So I will try a ground on the light to see if maybe it broke somewhere along the way and another switch.
Incidently I have found a wire coming off of the trailer hookup that has power when the breaks are applied, doesnt when they are released. This wire was not hooked up to the plug but was in the harness taped off.
Either way I totally apreciate the help that I have recieved and will donate as much as I can when I can. Thank you
kevin
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Sunday, December 28th, 2008 AT 5:28 PM
Tiny
KEV3W2H
  • MEMBER
  • 8 POSTS
I WOULD LIKE TO THANK ALL OF YOU FOR YOUR HELP. IT TURNS OUT THAT THE HAZZARD SWITCH WAS FAULTY. I WAS ABLE TO REPLACE IT WITH A USED SWITCH AND HAVE ALL MY LIGHTS BACK.
I WILL BE USING THIS SITE IN THE FUTURE FOR MY QUESTIONS.
THANKS AGAIN
KEVIN
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Thursday, January 1st, 2009 AT 3:28 PM

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