All lights work except brake lights

[hambo]

Hey GM squarebody,
I recently picked up a 1987 v20 and I have an electrical question. The taillights work, as well as the blinkers, although they do blink fast/irregular speed. But I cannot get the brake lights to work. Meaning when im braking, the light bulb doesnt illuminate and get brighter. I checked the fuse and its good. And I dont think it could be a ground issue because the light bulb still works as a blinker and running light? Both of the brake lights on either side dont work. Neither do the reverse lights but im not too worried about those. Could the brake light switch at the pedal be bad since they both dont work? Thanks in advance!

 

[87sierra]

i would check the brake light switch by either checking the resistance using a multimeter if you have one or i believe you can jump the plug and see if the lights light up then it is a faulty switch if not it is either in the wiring from the switch to the lights also there should be a round plug behind the bumper with four wires going into it this is for both tailights it could be that the pins inside the plug are corroded causing poor to no connection

 

[hambo]

I checked the four wire plug today and they all looked good. Still gotta go buy a multimeter to check the rest. Sorry if this is a stupid question but what do you mean by "jump the plug" ? I have very limited electrical knowledge.

 

[87silveradok20]

I checked the four wire plug today and they all looked good. Still gotta go buy a multimeter to check the rest. Sorry if this is a stupid question but what do you mean by "jump the plug" ? I have very limited electrical knowledge.

i think he means run another power to the wire on the output of the plug

 

[350runner]

I had this same problem. It ended up being the hazard light relay. I pulled it out and trapped it on the truck bed pretty hard and I've had break lights ever since.

Sent from the dust in front of you!

 

[hambo]

Okay. Maybe I'll try that! But my hazards work currently. Did your hazard lights not work?

 

[350runner]

Hazards did work at the time.

Sent from the dust in front of you!

 

[350runner]

Have you tried bypassing the brake switch? All that is remove the two wires and connect them with a paper clip or something.

Sent from the dust in front of you!

 

[hambo]

How would I do that? Wouldnt I have to cut the wires? And I have very limited electrical knowledge so where was the hazard light relay located on your truck? Thanks for your help

 

[GTME94]

One other thing to think about is that the power for the brake lights goes through the turn signal switch. The brake light and turn signal light power the same secondary filament of the bulb.

If the neither of the turn signals is on, the brake light power from the brake switch goes to both Left and Right rear bulbs. If you have the left turn signal on and then press the brake, the turn signal switch interrupts the brake light power to the left bulb so that it blinks and vice-versa for the right turn signal. If you don't have the brake pressed it sends power to the proper bulb for the turn signal.

I had a brake light problem this summer where my left brake light didn't come on at all. I had to replace the turn signal switch and now both brake lights work fine.

Changing the turn signal switch is kind of a pain because you have to remove the steering wheel and take apart the top part of the steering column but it's not that hard. There is a good thread on here to walk you through it if that's what you end up having to do.

 

[350runner]

Start with the brake switch under the dash. It is located just above the brake pedal.

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Sent from the dust in front of you!

 

[87sierra]

by jumping the plug you eliminate the swithc kinda like putting a paper clip in the supply power to the outlet side of the plug that goes to the brakelights is what i mean

 

[hambo]

so would I just use a paperclip and jump the two inner prongs on that switch? Which prongs do I have to connect out of the 4 from the picture in post #11?

 

[350runner]

Unplug one connector at a time. Put a paper clip in the two connections. The brake light should light up if the switch is the issue

Sent from the dust in front of you!

 

[hambo]

Checked the brake light switch and the lights didnt light up even when I connected them with a paperclip. so that rules out it being the switch. So I guess I'll check the hazard relay if I can find it and the wiring too this weekend.