I just received my car back from Ernst at RX7 World (engine rebuild, etc). Since I got my PFC, I have had the typical situation that my A/C doesn't work in the number 3 fan position (and I have not had time to try the many "fixes" listed out here). Anyway, since it came back, it is working perfectly in all fan positions. The only thing I can think of is that I had a new wiring harness installed in that the old was just getting too brittle to work with. Think this could have fixed it??
--Jeff

 

A new harness solves many problems, known and unknown.

 

Mine was just the opposite. My old wiring harness worked great with no AC issue. Got a new harness and had to ground the switch to get the AC to work.