I just got off the phone with FAST Tech Support, and they told me their documentation is wrong for their AC detect input.
I've been wrapping up my Vintage Air install, and that meant I was working to integrate my ECU with the AC. The XFI box supports max temp and max TPS for AC clutch enable (so when the car gets hot, or you're at WOT the AC compressor gets turned off).
It also supports AC detect, so you can have the ECU raise the idle speed when the AC is on. Well... before I put all my interior back into place, I was testing those circuits and I couldn't get the AC detect circuit to work. The documentation says to pull pin A24 to ground when the A/C switches on. That just didn't work, and I pulled my wiring apart trying to figure out why. Finally, I called FAST this morning to get an RGA number so I could ship the box to them since I was sure I'd burned out the ECU or something.
Anyway, the guy goes: "I have some notes here about that...".
You are supposed to send pin A24 12V when the AC is on, not pull it to ground.
FAST is working to correct their documentation.
I thought this might save some time for folks trying to get their AC detect circuit working.
jp