In the HOT HOT HOOOOOOT Vegas desert. A/C is not blowing ice cold. Checked recharged system, but A/C clutch stays engaged at idle but only runs for a few second intervals if rpm is above 2,000 any ideas on cause/fix? Figure clutch is not staying engaged enough to move the freon. A/C was evac'd/recharged and converted to 134A as I though the system might have been low, but that wasn't it. All original parts and issue remains. 92 5.0 GT 141K.