ok symptom, a/c haven't been used in 5 years, I just recently decided to get it working since I'm going to daily drive it. I do have powerfc installed.

1. the a/c freon is filled and vacumm checked, no leak
2. at the mechanic's shop, we couldn't get the compressor to engage on any a/c fan setting, when looking in the powerfc sensor screen, the a/c dot was always off.
3. we connected power to the compressor plug and it turned on immediately, we had to do that to fill in the freon.
4. so we know the problem is not compressor or freon level related, it's somewhere in the control system.
5. i know the a/c fan switch is a problem on powerfc, but usually it still works on 1 and 2 setting, mine doesn't work in any setting. how do i know if fan switch is the cause?

so my quesiton is how do i begin to diagnose the a/c system? I'm a noob on electrics, so i kind of need a detailed step by step

 

After you make sure that the 15amp a/c fuse under the hood is ok, unbolt the front plastic relay box (2 bolts) turn it upside down and take off the bottom cover, exposing the relay wires. Check the larger yellow wire on the a/c relay for power.
That wire should be getting power from the fuse block. If not, splice a new wire from the underhood fuse block to the a/c relay.

 

Search in the PowerFC forum on this topic - it's been covered to death. The fan switch has been one culprit, and one person just found the temp sensor in the evaporator is another culprit.

This is a pretty tricky electrical problem, and it's stumped a lot of people. There are some hacks/workarounds for the problem that take the ECU out of the loop as well. Again, hit up the PowerFC forum for more info.

Dale