'94 Civic hatch, Canadian edition CX (A/C, power steering, auto, factory D15B7, girlfriend's car).

AC light comes on, idle drops, condenser fan turns on, compressor doesn't.

Switched condenser & compressor relays, no change.

Tried measuring voltage between the red wire going to the compressor & body ground, 0V. Measured continuity between the plug at the compressor & red wire connection at the relay plug, and it's good. Accidentally measured voltage between the compressor-side plug and ground, and I think I remember reading a low voltage? I wish I had the car here to double-check.

Followed the diagnostic procedure from pg. 22-9 in the manual, and everything checks good except the thermostat, up until measuring pulley clearances and such (not checking the compressor until there's voltage going to the compressor).

The manual says the thermostat is a two-pin. We have a 3-pin?

There's the proper BLU/RED and YEL/WHT wires according to the electrical diagram in that section, but also a YEL/BLK or vice-versa (I should've taken pictures). The 3rd wire has 12v to body ground with ign on and car off. I forget the order of the other two, but one had 12v to ground, and the other had 10.5v to ground? There was continuity between the YEL/WHT and BLU/RED pins on the t-stat. The 3rd pin was open between the two. Maybe it's just a heater?

Jumpered the YEL/WHT and BLU/RED connectors with no change to compressor red wire voltage.

I want to briefly jump 12v directly to the compressor to make sure it's working, I just didn't have wires with me at the time.

Right now I'm thinking it's a problem with the BLK/RED wire to the ECU, the ECU itself, or the RED/BLU wire between the ECU and pressure switch.

Thoughts? And what's up with the 3-pin T-stat?