Saab: A/A problems, compressor clutch, strange smell

Question
i have problems with air conditioning in my saab convertible. after starting the car the aircon works fine for 5 min, then you get a strange smell and warm air starts coming out fans. sometimes the cooling comes on again for a short wile. system has been regassed which did not solve the problem. my mechanic now says it is probably the clutch in the compressor...what can you advise me please?

Answer
Michele:
 
 When the compressor clutch fails, it is usually quite noisy...as there is metal-on-metal slippage; you did not mention any noise. Another possible way for it to fail is that the electrical solenoid circuit loses contact after it is on for a while,and heats up. One way to check this is to observe the a/c operation when it is in the failing mode with the engine running. The entire clutch pulley should be rotating in order for the a/c compressor to operate. If not, then either the clutch has failed (as above) OR the computer is not providing a signal to the clutch. You can test this by providing 12 volts directly to the clutch solenoid; if the clutch turns on and stays on...its the control computer. Otherwise, it is the clutch as noted above.
 Hope this helps,
                 Jerry