This is making my brain hurt..

[Konas new ride]

I have a 80 gmc 3/4 ton.. I have no brake lights.. Tail lights work.. those little marker lights work.. I'm getting nothing back there for power for the tail lights. Both filaments work in the bulbs. My wire diagram says light blue for wire color. That's a lie.. I see yellow, light green, green and black. Any hints before i go poking holes in the wiring under there with my tester? I did try to find the color codes on this site. I just can't find them..

Thanks guys...

 

[marks86]

I have to assume you checked the brake light fuse, along with all others

 

[J Knight]

Do the blinkers work? If so you are getting power to the rear for the brake lights to work. Check your brake light switch under the dash. You can unplug the switch and use a jumper wire to quickly check to see if the brake lights come on indicating a bad or poorly adjusted switch.

 

[Konas new ride]

I have to assume you checked the brake light fuse, along with all others

I can't find the dang fuse.. so im just about to go check em all.

 

[marks86]

check them with a tester not just eyeball

 

[Konas new ride]

0Ohh i know.. The piss off is i can read a wire diagram, I know electronics very well (i'm a ex top drive mechanic half of that is electronics... Just nothing is matching from the book (gmc book) to the truck. I don't want to start undoing much or the rest of it wont work. I should have stuck to doing yard work today.. sure glad i only had one beer this morning.
Fuses are good. Checked em with my fluke. any idea on that wire color?

 

[Konas new ride]

Do the blinkers work? If so you are getting power to the rear for the brake lights to work. Check your brake light switch under the dash. You can unplug the switch and use a jumper wire to quickly check to see if the brake lights come on indicating a bad or poorly adjusted switch.

SWEET.. I was eyeballing that sucker.. I have both signals at the back..

Thanks everyone. I will go try this right now...

 

[Konas new ride]

WEll.. That may take some loving to get out. The switch does open and close..

 

[Konas new ride]

Okay.. a pair of reds on one plug and a orange and a white on the other plug. With out ripping the dash out i can't see where this stuff goes.. Any clues?

 

[Konas new ride]

Do the blinkers work? If so you are getting power to the rear for the brake lights to work. Check your brake light switch under the dash. You can unplug the switch and use a jumper wire to quickly check to see if the brake lights come on indicating a bad or poorly adjusted switch.

So.. I have both back signals. I ran a jumper.. Nothing in the back turns on for a brake light. Does this mean time to rip the dash apart? I hope not.

EDIT.... TO ADD TO THIS....



If i am reading the wire diagram right.. This white wire goes up into the steering column off of the brake switch?

 

[bluex]

If the turn signals work but the brake lights don't your turn signal switch is bad. Same thing happened to mine.

 

[robert8096]

Check for power at the wires at the brake switch. If you have power on one of the wires. If you have power on one then do a continuity test on the wire without power. This wire should be the one feeding the rear brake lights. If no power on either then you will need to figure out which wire goes to feed the rear and trace the other wire back to a power source.

 

[Konas new ride]

If the turn signals work but the brake lights don't your turn signal switch is bad. Same thing happened to mine.

Check for power at the wires at the brake switch. If you have power on one of the wires. If you have power on one then do a continuity test on the wire without power. This wire should be the one feeding the rear brake lights. If no power on either then you will need to figure out which wire goes to feed the rear and trace the other wire back to a power source.

Thanks guys... I didn't see your posts before leaving.. but i do want to thank everybody.. The white wire from the brake switch does go up into the column. The white wire had been pulled out of the plug at the bottom of the common but you couldn't tell.. so it would work if i hit a bump.. then not work on the next bump. I pulled the pin out the plug reattached the wire inside the pin and reconnected.. AND.. BRAKES... Again.. Thank you all.. Some times i just need to see infront of me a route of workings for stuff.. This forum is a tremendous help.. You ALL rock..




Pretty mushsy coming from a 45 year old huh.. hahaha

 

[robert8096]

Glad you found the problem.

 

[Konas new ride]

Thanks Robert. Now if it rains i can get to town with out unhookling my work trailer from the cummins.

Love this ole truck.. next is the cargo light.. Then getting the door pins working and changing out the door tumblers..