1990 Mercury Grand Marquis GS mileage: 91,000. When the air conditioner is on and the car is running at 60 MPH, the air-conditioner blows very cold. In traffic with stop and go it starts blowing hot. I have replaced compressor, clutch, dryer, condenser and also installed inline filter. When in traffic, temperature gauge climbs and then the air conditioner will blow hot. Is there a limitor switch or something that cuts the air conditioner out when the temperature gauge gets to a certain point? Any ides of how I can fix the problem. I live in Arizona and it's very hot here.
Check the cooling system, particularly the radiator to make sure it is not partially plugged. Additionally, check the radiator fan for proper operation. If the engine temperature is running way above normal, some of the heat is transferred to the air conditioning condenser, which causes the air conditioner to lose efficiency. As for your question about a "limitor" switch, there is a high pressure switch in the air conditioning system that cuts the compressor out when the pressure gets too high.