1997 GMC K2500 Suburban - no brakes in Z82/UY7 tow harness

[MartyW]

I went to replace the 7-pin RV plug and old trailer plug wiring in our newly-purchased '97 GMC K2500 Suburban 7.4L. The 7-wire UY7/Z82 harness is in place and was in use by the previous owner but there is no brake signal in the green and yellow wires that carry the turn signals in that tow harness. I have the service manual and according to the manual everything looks correct to me, except that no brake signal is carried in the green & yellow wires that the manual says carries brake + turn signals.

The tail lights on the Suburban work perfectly with strong signals for brake + turn.

I'm studying the wiring diagrams in the service manual and have found the stop/hazard switch in the drawings and the output from this switch seems to be the green & yellow wires that go to the tail lights and are spliced (somewhere) to also feed the tow harness green & yellow stop/blink wires.

Questions:
.) Where is the stop/hazard switch and what does it look like?
.) Someone mentioned splicing at the tail lights, and I've done this in the old days when one bulb did full light/stop/blink duty, but is splicing at tail lights even an option with the '97 Suburban since there are multiple tail lights on each side?

All help/advice greatly appreciated.

Edit: I did have a few minutes today to pull the tail light assys, and each has a 4-wire harness and sure enough - left/Yellow & right/DkGrn are wires in the left/right taillight harnesses and these wires have the correct brake+blink. So, if we can't figure a correct way to get brake feed into the tow harness, I do have the option of pulling those feeds from the left & right tail light harnesses.

Thanks,
Marty

 

[inthechateau]

There is a feed in the rear light harness that traverses left to right side above the rear bumper area. You might need to drop the spare to get to it, but look for the flex conduit up under your rear roll pan. Kind of hard to get your hand in there but that is where a feed is usually hooked up for trailer harness. Sounds like you have a bad splice or wire lock up there.