I have a 2001 Tahoe with rear a/c problems. The orange power wire is intermittent. Some times it works like a champ and other times no power at all. I have replaced the rear fan blower and resistor and it didn't help. I have traced the orange wire to the passenger side dashboard and it doesn't seem to have a short. Any ideas ?

 

Relay in that circuit ? Could be bad connection at fuse in fuse block, GM has issues in fuse blocks, look at the backside of the fuse block at it's fuse for signs of overheating.

 

It goes into the main fuse box under the hood, I can see the wire going into the box. I don't have any idea how to loosen the main fuse box to look under. Any ideas ?