im stumped

[Dirtkid93]

ive had brake light problems since the day i bought the truck, i replaced the bulbs, sockets, brake light switch on the pedal, checked all the fuses and connections, and I'm still left without brake lights, only running lights, am i at the last resort of buying a new wiring harness for the rear end?

[siggyfreud]

Do you have a voltmeter and a 2x4 or friend to depress the pedal? I'd pull the bulb and check for voltage with the pedal down. I'd guess you're not getting any and there is a break in the wire somewhere.

[64-454ss]

Double check that the bed is properly grounded. Preferably with an actual ground strap and not rely on just the bed being bolted to frame. I was chasing same problem on mine and bad ground was the culprit.

[TopFuel1966]

Use an ohmmeter and measure for continuity between the connections on the brake switch. When you push down on the pedal it should show as a closed circuit. If not adjust the switch so that the pedal drives the switch plunger far enough to make a circuit through the switch. If you have running lights the ground is probably ok but still not a bad idea to strap the light buckets to the bed and ground the bed to the frame.

[Vernski]

Originally Posted by 64-454ss

Double check that the bed is properly grounded. Preferably with an actual ground strap and not rely on just the bed being bolted to frame. I was chasing same problem on mine and bad ground was the culprit.

X2 on the bad ground these truck were notorious for ground problems especially the boxes, here is some info for GMC's but most of the wiring is the same except a few GMC specific items. Lots of good info in this link...Vernski

http://6066gmcguy.com/wire-tips.html

[PGSigns]

Well since the running lights work and the brake lights dont I think the grounds are ok. Do the turn signals work? The brake lights run through the turn signal switch and that could be an issue.
Jimmy