Galaxy models of this age can be a bit of a problem trying to sort out the a/c system as there are a few variations of wiring circuits.The a/c compressor is controlled by 2 relays.One is the wot (wide open throttle) and the compressor relay.Unfortunately there is no designation on the relay board as to which does what.I don't quite understand the fact that the a/c works if the pressure switch is bridged?This tends to suggest that the rest of the circuit is ok or perhaps there is inadequate gas pressure in the system.There is no way a main dealer could fix a car this old as the system has no diagnostic function.It needs a techie to follow the correct wiring diagram and work through the circuits step by step.Is this car fitted with climate control and/or auto transmission?This also makes a difference to the circuit operation.

The pressure switch on these is a dual function device.It will switch the a/c system off if it detects insufficient gas pressure,to prevent the compressor operating .It will also bring the cooling fans on high speed if the gas pressure gets to a pre determined high value,usually max a/c cooling in high ambient temp conditions.If the system works ok with the switch bridged out,then the rest of the circuitry must be ok,including the relays.A possible situation is that the switch is not "reading " the pressure correctly.It could be that the pin in the centre of the switch is not depressing the schraeder valve adequately in the filter drier,or the valve is faulty,so it can't see any gas pressure.I would be taking a close look at the screw on fitting on the drier.hth

Thanks again guys, I suspected as much to be honest, I never had much faith in the relay hypothesis. I will turn my attention to the sensor / drier / pressure switch situations and get back with news.