Originally Posted by dsvw

Original poster here.

My pressure and temperature switch have been tested and are working fine. My auxiliary fan is operating when I attach 12v to it, and both relays have been tested (and swapped out with 4 different relays each). The system has a new compressor and has been vacuumed. It has had the proper oil and refrigerant added by a professional a/c tech who works on these vintage a/c systems. The air will blow cold if I am driving highway speeds. When I slow down and sit in traffic in the 90+ heat we have been having, the system and condenser heat up and cannot be cooled because the aux fan is not coming on.

I have determined that there is a problem in my a/c wiring that is not allowing the auxiliary fan to operate as designed. Everything else tests fine.

I have ordered the switch from Rollguy that will bypass some of my a/c wiring and turns the aux fan anytime the compressor comes on.

I'll report back.