1991 940 turbo USA. Works good for 2-10 minutes then doesn't, at random, when going 55mph or faster. Seems to work continuously at slower speeds like 35mph.
A/C compressor and clutch are good, belt new and feels as tight as the other belts. Freon (R-12) measures good pressure on the low-pressure side and the dryer is real cold to touch.
It does not have electronic climate control,or any numbers on the A/C knob. Don't know if it uses a cabin temperature sensor. Just turn left(blue)for colder, or right(red)for hotter.
Any ideas? Thanks, ...Al...

Hi,

These could be due to increased compressor clutch gap. There is an air gap in-between the pulley and the centre spindle plate of the compressor. The gap should be around 0.019 inch (0.5mm) measured at the rim (outer diameter) of the clutch. Use a feeler blade to do this (when the engine is off). If the gap is more then this might be the culprit.

A temporary fix could be done by using plastic bread clips (used to seal off bread wrappings). Please go to http://www.matthewsvolvosite.com/2000-s70-question-about-ac-compressor-shim-fix.html

A permanent fix would be to take off the centre spindle plate which requires a special tool because the plate can be very tightly fixed to the spindle. Replace the centre washer with one having the correct thickness and reassemble the plate. Better go to an aircon shop to do this.

Hope this helps.

amarin.