VR6 air con and radiator fan problem

[rochford]

Hi, I have a 2 problems with my Golf Mk3 VR6 Auto (1997). I think the problems are related. When my engine is hot and I have the air con/climate control on, the air con compressor whines when pulling away, if I press the Econ button, the whine stops immediately. The 2nd problem is the temperature gauge will rise to 100 when sitting in traffic, at which point the fan cuts in on max speed to cool it down in seconds, to its normal 90 degrees.
I can't get the fan to cut in at a lower fan speed or temperature, I've been told the fans 3 speeds are working ok. My question is: should the fan be running when I have the air con on? If so, what could be faulty? I have changed the coolant temperature sensor unit (G62) in the thermostat housing, but it's made no difference. The 2 fuses above the battery are ok, is the radiator temperature switch a replaceable unit? and where is it?
Any help/replies appreciated.

[Crasher]

Yes, the cooling fans should run with the A/C on. If the screeching stops on ECON I suspect your A/C compressor is partly seized.

The switch is screwed into the radiator but a pig to get at.

[rochford]

Thanks Crasher, Is the switch set into the top side of the radiator, and indented?
Does the compressor come out the bottom of the engine bay, and does it have serviceable parts?

[Crasher]

The rad fan switch is low down on the cars left of the radiator pocking out through a hole in the front panel. You need a deep 30-mm socket.

The compressor comes out from below, MUST be professionally discharged before removal and is not repairable.

[rochford]

Thanks for that. I have ordered a new radiator fan switch from vw Leics, will pick it up later in week and fit at weekend. Then I can see what the air con compressor does!