Some files below that should help. Right click and save as. Hope they help.

Aftermarket Wire Harness Schematic
Step AC Troubleshoot
GM AC Schematic

 

Hey man thanks alot!!!!!!

 

I had the exact same thing happen to me last nite, Got the fans on. They come on at the desired temp however it seems like the A/C will not kick on, even with defrost. So what is up with this problem?

 

Has anyone figured out anything on this yet? The truck only has 19k on it and the air has always worked fine. I cannot even get the defrost to kick on the compressor.

 

I am still working on it I really have no clue and I thought I was pretty good with wiring. I will keep you posted. I called Allen Nelson but he has yet to return my call and I called him I think Thursday.Also let me know if you find out anything.

 

I'd say unhook the Nelson harness from the AC feed to rule it out? Also verify that you are tying into the DK Green wire to the compressor. Wire 59 in the AC schematic I posted above. Works just as its supose to on mine.

 

Here is a photo I outlined where the to find the green wire. Traced the wire loom in yellow and circled in yellow where I tied in. You can see the tape where I secured it when done.

 

KY- That is exactly where mine is tied in at, did some more playing around today, It seems like the defrosters are working. The thing that I am not sure of is the fan only kicks on high for a couple seconds when the defrosters are turned on, I was under the impression that one would stay on high the whole time the a/c was being used? Also, tried unplugging the a/c tap and makes no difference in how anything works.

 

One of the fans will kick on high ONLY when there is power to the A/C clutch. (Green wire) The right fan is kicking on and off (high) with the def or A/C on, but can you see the A/C clutch is not turning?
If that is the case, the wire tap used to tap in to the green wire may have cut the wire in two. Unplug the pig tail at the A/C check for power at the tap and at the A/C plug. (Move the wire around were the tap is during test)
If power is at both places the problem is on the ground side of the A/C clutch.
But if you have power at the tap but not at the A/C pig tail the wire is cut................... somewhere

 

As WR said the right fan will run on high for the same amount of time the A/C clutch/AC is on. It's purpose is to too cool the A/C condenser while idling in traffic and keeping the A/C cold when not moving. With the defrost in winter it will only come on for a couple seconds and then back off. Aggravates the pee out of me especially when cruising down the road and you don't need it.