If I turn the AC on to low or medium speed the blower kicks in for 1/2 a second then stops. If I turn it to high it works fine right away, and once I've had it on high I can go back to medium or low and it works fine.

any ideas? This is on a '92 XJS.

 

I've run into that a few time over the years. Even saw it a time or two on the later years of the XJ40. I think the only truly permanent solution is to replace the A/C control module. That is an expensive proposition, though. Several folks have just elected to put up with it.

Cheers,