A/C doesn't work while stopped

I have a 05 pt convertable. The cooling fan doesn’t come on reliably with the A/C compresser, and then eventually the pressure relief lifts. When on the hyway and the at speed it makes good cold air. The Fan works fine w/ Engine Temp. How does one fix this.

As with all automotive AC problems, I suggest you take the car to a garage that specializes in automotive cooling and AC systems. They have all the necessary equipment and expertise to diagnose and repair your car’s Air Conditioner.

More succinctly, what relay and or switch should turn on the main engine cooling fan while the A/C compressor is running?

The most likely cause is a malfunctioning pressure transducer. I think its a dealer only part that cost over $100.00. So its probably best to have it diagnosed, and repaired at the dealer.

The car’s computer reads the actual refrigerant pressure from the pressure transducer, and cycles the fan to maintain optimal pressure.

I think you have a common problem. The engine cooling fan must come on in order to cool the AC condenser. The condenser provides cooled refrigerant for the compressor. I would have the engine cooling fan checked out. That’s why the AC works normally at highway speeds. The engine cooling fan is out of the loop at this point.