Hamstertree, I know this thread was from about 2 weeks ago, but I wanted to check in with you on your troubleshooting if you haven't figured it out already. The 13V reading with the A/C switch off is certainly cause for concern and sounds like a short circuit somewhere. I would look into isolating the cause of that first and it may correct the whole compressor clutch issue. The BCM is looking for a value of 5 on that input signal to detect that the A/C switch is off and likely is confused by an input value of 13. Looking at BCS-13, which you referenced, the two wires in the BCM harness adjacent to the A/C switch input both supply system voltage levels, with pin 28 (pink wire, blower motor circuit) constantly at system voltage and pin 26 (green wire, thermo control amp) intermittently pulsing to near system voltage then dropping to 0V, potentially implying a damaged or mis-pinned BCM connector. If everything checks out on the BCM connector side, check the same circuits coming out of the A/C control head (front air control).