I have been trying to get my ac back working for a while, my ac compressor won’t come on neither was my blower, I manage to fix my blower, but the compressor is still not coming on, and here is a list of things replaced:

1. Ac main relay.
2. Ac pressure switch.
3. Refill and pressure check system.
4. Fuses related to ac.
5. New logicon with amp box.
5.New blower and relays related to the blower.

The compressor will work if direct current is applied, but I wonder what else could be replaced. Thanks.

 

Seek help from a technician and you might find help from him to your problem.

 

Best I can do, check troubleshooting section:
http://www.13betc.com/images/article...AC_Systems.pdf

 

Is it a S5 FC (89-91), and are you running the stock ECU and factory wiring harnesses? I think this may also be true for S4 FCs but I'm not 100% sure. If not (e.g., you're running an aftermarket ECU), you'll need to do a wiring tweak to get the AC compressor to engage. The factory ECU basically acts as another series switch in the circuit that energizes the AC compressor relay (in series with the AC pressure switch you mentioned and a thermal switch on the evaporator core that you didn't); the idea is that when you floor the throttle, the stock ECU cuts off the AC for a few seconds to improve acceleration.

Anyway, if any of this applies to you, get the factory wiring diagram and you basically have to splice two wires that were on the factory ECU harness together.