1992 Chevrolet Truck brake lights not working

Tiny
STENNY
  • MEMBER
  • 1992 CHEVROLET TRUCK
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 145,000 MILES
I have replaced brake switch and tested brake switch wires and when brake is applied the purple wire gets power. From what my repair manual says it should be the white wire but white wire seems like a ground if I use a test light between the 2 test light lights up. I have been trying to figure this out and can't seem to figure out what is going on here also on the brake switch the orange wire has ben disconnected and I am not sure where to connect it or if I need to.
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Tuesday, November 17th, 2015 AT 5:47 PM

8 Replies

Tiny
CJ MEDEVAC
  • EXPERT
I'M GOING WITH YOU MAY HAVE A BAD GROUND TO THE LIGHTS

THE REASON SOME OF THIS MAY WORK (EVEN DIMLY) IS ONE WIRE IS SEEKING ANY KINDA GROUND THRU IT'S NEIGHBOR WIRE.

I SEE THIS HAPPEN A LOT WITH THE LIGHTS ON TRAILERS

I HAD TO SCREENSHOT THE UPPER AND LOWER HALVES OF THIS DIAGRAM AS "PRODEMAND" WOULD NOT LET ME COPY IT

LOOKS LIKE BLACK IS THE GROUND (THE RIGHT SIDE OF EITHER DIAGRAM IS THE BRAKE/ TAIL LIGHTS)

AS A TEST, YOU MIGHT RUN A TEMPORARY JUMPER WIRE FROM GROUND, TO THE BLACK WIRE TO PROVIDE IT WITH A "FOR SURE" GROUND, TILL YOU CAN FIND THE "OPEN" ON THE ORIGINAL CIRCUIT. IT MAY EVEN LOOK GROUNDED, LOOSEN THE ANCHOR AND SCOOCH IT AROUND OR CLEAN THE AREA.

YOU SHOULD BE ABLE TO SEE WHERE DIAGRAM ONE OVERLAPS DIAGRAM TWO

THE MEDIC
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Tuesday, November 17th, 2015 AT 7:19 PM
Tiny
CARADIODOC
  • EXPERT
Better find a spot for that orange wire because that's where the 12 volts comes from. That will show up on the white wire when the brake pedal is pressed. It's acting like a ground now because you're finding a path to ground through the signal switch and brake light bulbs.

The purple wire is part of the anti-lock brake circuit. That uses a different part of the brake light switch.
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Tuesday, November 17th, 2015 AT 7:20 PM
Tiny
STENNY
  • MEMBER
There are 3 flashers 2 near firewall and 1 behind fuse box. There is a 2 prong flasher behind fuse panel which controls blinkers, theres a 5 prong and a 3 prong flasher under dash near firewall. I am not sure what does what with those flashers or relays I would imagine the 5 prong does brakes etc mine lookalike 2 prongs are burnt probably from my having wires crossed at the rear of the truck

brown wire also get power when brake is pressed the brown wire is on the 2 wire connector on brake switch and goes towards firewall it seems like it goes behind relate panel

there is power coming in from 2 wires I think they were red. So I think I may have found the other part of the orange wire but when I hook it up to the brake switch it makes my passenger taillight stay on even when key is off and brake is not pushed so I don't know why that is but its the only orange wire I ave seen so far.
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Tuesday, November 17th, 2015 AT 8:05 PM
Tiny
CARADIODOC
  • EXPERT
The orange wire comes from the Brake light fuse in the fuse box.
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Tuesday, November 17th, 2015 AT 8:23 PM
Tiny
STENNY
  • MEMBER
Ok why would it make my passenger taillight stay on even when the truck key is not in ignition?
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Wednesday, November 18th, 2015 AT 6:39 AM
Tiny
STENNY
  • MEMBER
I am going to replace relays and flashers today and see what happens. My hazards stopped working but my turn signals and parking lights still work
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Wednesday, November 18th, 2015 AT 6:40 AM
Tiny
STENNY
  • MEMBER
I will let you know how I make out after replacing the relay and flashers see if brake lights work
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Wednesday, November 18th, 2015 AT 3:51 PM
Tiny
STENNY
  • MEMBER
The orange wire kept brake lights on because I think spring in brake switch is messed up because it doesn't shut off taillights I tried adjusting it for like 20 min and no matter what I did brake lights stayed on when you let off the brake pedal, I would need to pull adjuster up to make brake lights shut off. Maybe I am adjusting it wrong idk anyone have some advice or can someone make a video of how to adjust brake switch that would help.
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Thursday, November 19th, 2015 AT 10:08 AM

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