Can't get the AUX fan to come on. Troubleshooting now but wondering if I'm overlooking anything obvious. The fan worked in the last truck and spins freely, Fuse 5 and 6 are good (although 5 was blown so I replaced it, still good). Horn worked so I swapped that relay with the fan relay, horn still works. I get continuity to ground on Pin 2 at the fan connector. I do not get 12v at pin 1. No charge in the system presently but I jumped out the Hi/Lo switch at the drier and the compressor kicks on when I set the HVAC panel in auto and the temp at 60°. Is there something else I should be considering or are there any common failure points here?

My next steps are to pull the fan relay, start the truck and turn on the AC to check for
1) 12v at Pin 30
2) ground at Pin 86
3) jump Pin 30 to Pin 87 to see if the fan comes on

Assuming this check out I think that points to the ECU or the HVAC panel itself not supplying ground to the fan relay? Since the engine isn't in a hot condition at the moment I think the ECU would not be providing ground and the HVAC panel should. The panel in the parts truck ran the AC so I can retrieve that one of these days and try that. Anyone else been here? Is there a key piece of this I'm missing?

 

Ignore this post. Reading is fundamental. I was swapping the horn relay for the AC relay (R11 for R12). Once I swapped the washer pump relay for the aux fan relay (R4 for R3) the aux ran roared to life.

 

Good job!