My friend's '95 Previa LE SC has the following problem. It seems very weird to me and cost to repair is $1100 from an independent shop.
"I do know that the A/C cools just fine until the engine gets really hot as in stop and go driving. If the car is sailing along no problems. But if the engine is hot as in multiple stops when doing errands to the store then something happens at that point and the cool stops in the front A/C. The rear still blows cool. The A/C shop said I have a constriction flow problem. No freon leak was sniffed and dye test was ok (NO LEAK-really weird).
Compressor doesn't seem to cycle fast. It seems to stay on for long periods.The guy at the shop said because of the constricted flow, ti wouldkeep the oil from the compressor and it will cause premature failure.
They completely drained the coolant and re-filled and it was almost exactly the amount they drained out. I don't see any bubbles or foam in the sight glass. And the A/C will work fine initially for even an hour of straight freeway driving, but put strain on the engine or stop the vehicle and get back in or be in stop and go traffic and the front quits blowing cold air........"
Matt