I'm doing some early diagnosis to determine why my AC doesn't work. (It never has.) I have a Sanden compressor, and it appears to me that it may not be electrically functioning. I can't hear anything engaging (no click of the compressor clutch, nothing) when I turn on the AC. Makes me think the compressor clutch isn't getting any power. Or something. I've run a meter between the "power line" (at the power terminal on the compressor) and a common ground, and it's getting nearly zero volts. So now I'm trying to trace where the power comes from, up the chain. Maybe the wire is needing full replacement. But, as I haven't taken the whole thing apart, wires are buried under hoses and I can't tell what is connected to what. Right now I'm just using a mirror and my fingers to "feel the path". So, please see pic. Does the "blue junction" connection in the pic (which is connected to a tube on the plenum?!) provide the power to the AC compressor? If not, where does the compressor power line feed to in the engine bank? thanks Image Unavailable, Please Login
Blue connector has nothing to do with the AC. It for the cold start injector. Power to the black wire is controlled by the AC system pressure sensor switch. The clutch will not engage if there isn't sufficient charge in the AC system. You may be low on Freon or R134a, which ever your system is charges with, or the sensor could be bad.
John - excellent, thanks. I'll start tracing wires in a different direction then. I do get that the clutch won't engage under low charge, but I'm not convinced the unit has proper current either - as that black wire is showing no volts when I put it on the meter. What I mean is - even if the system has NO freon, shouldn't the power->ground show a good 12V output?
No. If the pressure is too low (or too high) there should be no power to that connection. You will not see 12V under those conditions. In addition, if the pressure is correct, the AC must be switched on and the thermostat set to max cool to check for 12 V at that connection.
AHA. Been chasing dog that shouldn't be hunting to begin with. Thanks so much, John... now it's making sense to me.
