so... update is I got down a Sanden 1242 compressor off a 2006 car; when I took it to the folks who "diagnosed" that the compressor was faulty, they discovered that the gas was low (turned out there was about 250g of gas, when it should be 650-700g). they also pumped it up with nitrogen and said there was a leak but they couldn't detect where from, and could be the evaporator housing (which means a dashboard removal).
How they came to the conclusion that the compressor was faulty when the gas was indeed so low is yet to be resolved, but I took it to another mechanic who was recommended by some people I know.
He disconnected the tubings and separately gassed up with nitrogen the evaporator, the compressor and the condensor - no leaks. he then put everything back together and checked, including soapy water on the joints, and there was a leak from the low pressure end of the compressor. Why the earlier guys couldn't spot it, is yet another question to resolve.
anyway, the double-lip seals that citroen use are not available (apparently even the pug dealership doesn't stock it) so the guy tested it with 2 regular rings of same diameter, and it seemed to be holding pressure. So we decided to charge it with gas, including the UV dye, and when everything was hooked up, the compressor didn't switch on. The guy fiddled with some wire (I thought it was the power to the compressor) but turned out it was the pressure sensor on the condensor pipes and the AC kicked in; gassed the system up and cool air was blowing from both sides - so would suggest that the flap motors are not faulty. (also subsequently another guy on UK forum had similar issue - warm on driver side - and a regas helped him as well).
however, driving home, I discovered the AC was not working so drove back - gas pressure still OK; but AC doesn't stay on - can hear the clutch kicking in, but almost immediately disconnects. as there cannot be abnormal pressure (390 PSI is the safety cutoff) and it's also not the engine temp (normal) it would appear to be a faulty reading from the sensor... I'm hoping it was just because it was disconnected when pressure testing the AC and that some contact cleaner will help it behave again. Otherwise I have to get it hooked on a lexia to figure where the cutoff signal is coming from...
thanks everyone for the help and advice so far!
How they came to the conclusion that the compressor was faulty when the gas was indeed so low is yet to be resolved, but I took it to another mechanic who was recommended by some people I know.
He disconnected the tubings and separately gassed up with nitrogen the evaporator, the compressor and the condensor - no leaks. he then put everything back together and checked, including soapy water on the joints, and there was a leak from the low pressure end of the compressor. Why the earlier guys couldn't spot it, is yet another question to resolve.
anyway, the double-lip seals that citroen use are not available (apparently even the pug dealership doesn't stock it) so the guy tested it with 2 regular rings of same diameter, and it seemed to be holding pressure. So we decided to charge it with gas, including the UV dye, and when everything was hooked up, the compressor didn't switch on. The guy fiddled with some wire (I thought it was the power to the compressor) but turned out it was the pressure sensor on the condensor pipes and the AC kicked in; gassed the system up and cool air was blowing from both sides - so would suggest that the flap motors are not faulty. (also subsequently another guy on UK forum had similar issue - warm on driver side - and a regas helped him as well).
however, driving home, I discovered the AC was not working so drove back - gas pressure still OK; but AC doesn't stay on - can hear the clutch kicking in, but almost immediately disconnects. as there cannot be abnormal pressure (390 PSI is the safety cutoff) and it's also not the engine temp (normal) it would appear to be a faulty reading from the sensor... I'm hoping it was just because it was disconnected when pressure testing the AC and that some contact cleaner will help it behave again. Otherwise I have to get it hooked on a lexia to figure where the cutoff signal is coming from...
thanks everyone for the help and advice so far!