Volvo Repair: Volvo 940 air conditioning, 1992 volvo 940, volvo 940

Question
I have a 1992 Volvo 940 SE fitted with air conditioning which doesn't work. By playing with control switches I can only get the compressor clutch to pull in if I short circuit the Low pressure sensor on the accumulator. Can I replace that switch without having a specialist in air con to drain and refil the system?

Answer
Chris, this is a common problem.  That pressure switch unscrews without having to drain the system.  Also on these, there are problems inside the control heads where some of the solder joints dont have a good connection and also make the compressor not kick in.  Roger