Volvo Repair: 2001 S60 Air conditioner problem, bump in the road, space inbetween

Question
Our 2001 S60 with 90k blows very cold air however intermittently it shuts off the compressor and blows hot.
Then we have to switch the A/C off for a couple of minutes then when turning it back on it blows cold again. Sometimes at a stop light it will shut off the compressor and blow hot.
I am thinking we have a bad relay/loose connection somewhere as it shut off today when I went over a bump in the road. Also it started this problem after a recent replacment of the smog pump, or whatever Volvo calls that component.
Where should I begin to look for a solution?
Thanks!

Answer
Steve, Whats happening is the clutch on the compressor is heating up and there is a space inbetween the clutch and the pulley.  This needs to be reshimmed.  If it this happens again, take a big pry bar and tap on the clutch and see if it engages.  I would also check the connector down at the compressor to see if its loose.  Roger