I just bought a '99 XJ. All seems OK but when the engine gets up to normal operating temp, the AC shuts off. Does any one know of a sensor or relay that might be the cause of this problem?

My '98 XJ a/c quits after about 30 minutes because it freezes up. To get it going again, I switch to vent for a few minutes, then I can go back to a/c for a while. It's a little low on refrigerant, but when you refill it it soon leaks back down to the present level. I just haven't had time to fool with it to find out where the leak is.

Yep! DB give it some refrigerant.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

Thanks Tom & Jim. Evacuated and recharged. Seemed ok for a while, then woulden't cycle back on. Checked pressures, HI & LOW were extreme opposite of what they should be, indicating a stuck expansion valve. This system does not have a replaceable expansion valve. After a while it worked again. Some say theese vehicles had many intermittent electrical problems. The A/C works more than it doesn't work making it difficult to diagnose which I would gladly pay someone to do if it would stay not working! <img src="/forums/images/graemlins/confused.gif" alt="" />

Uh, not replaceable? Then it must be CLEANABLE! But to take the system apart you will need to pull a vacuume on the system before recharging.. I'd advise a trip to the A/C guy.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />