Galaxy Quest

A local garage checked the pressure and all seemed ok but still didn't always work. When it does work its not a bad temp and it may work for 30mins, then nothing for a week. Can I test the pressure sensor with a multi meter? Would it show open circuit?

None of the posts I have found have the same problems. Most just don't work but I havent found any that are intermittent hence a new thread.

Please can anyone help. I have a 99/T 2.3 Galaxy which has working air con about 10% of the time. It is simple AC with dials and the AC light always comes on when you press the switch but nothing else does. When it works it's fine but thats not very often. If i put a supply to the compressor it works fine but as this bypasses all the safety devices I'm sure its not a good solution. Any help greatfully received.