BobG said:
The air conditioning on my 97 Volvo 850 cuts out periodically, but as
soon as I stop the car, turn off the engine, and restart it, the AC
turns on and works for 75 miles or so, then cuts out again. I have had
it fully charged and there are no leaks. Why is this happening and
what can I do to get it to work properly?
If your compressor has the thermo switch (at the end away from the drive
belt) short it out by removing the compressor electrical connectors and
reconnecting with the switch out of circuit.
If you don't have the thermo switch
Check the air gap on the compressor clutch, it should be about 0.3 - 0.5mm.
If it's over about 0.6mm it usually won't pull in once the compressor is
hot.
Adjustment is by removing the clutch plate and removing shims, this is not
possible with the compressor in situ as there is not enough end clearance to
remove the plate.
You will have to dismount the compressor, to gain enough room, I managed to
do mine with it still connected to the refrigerent lines but take care not
to strain the joints.
You will also need to make a puller to take off the clutch plate. The 3
tapped holes in the clutch plate are 5mm and the bolt holding the plate on
is 6mm. I fitted a longer bolt 6mm bolt and fitted 3 studs into the 5mm
holes. I then made a steel plate drilled to fit over the 3 studs so it would
pull on the end of the 6 mm bolt and pull the cluch plate off.
Once the plate is off be carefull not to loose the 1/2 inch shim washers.
Remove sufficient washers to reduce the air gap to about 0.4mm then refit,
the original 6 mm fixing bolt should pull the plate on again OK. Stop the
cluch plate turning while you tighten or loosen the bolt by using a
screwdriver wedged between 2 if the 5 mm puller studs you fit.
