Leaks, compressor issues, electrical / electronic faults.

Inputs that may affect A/C clutch operation include (but are not limited to):

1. A/C system pressure
2. Engine speed
3. Throttle position
4. Engine coolant temperature
5. Intake air temperature
6. Power steering pressure

If these sensor and switch values are either above or below the programmed operating range, the compressor clutch may not engage

Depending on the vehicle, additional items that may affect compressor operation could include:

1. A/C mode switch/actuator
2. Body control module
3. High and low pressure cut-out switches
4. Compressor clutch cycling switch
5. Refrigerant pressure transducer

Refrigerant leaks .

There are two types of refrigerant leaks in the automotive air conditioning system: Active leaks and Passive leaks.

1. The active refrigerant leak is a continuous leak. It doesn’t matter if the engine or ac system in your car is off or on hot or cold the refrigerant continuously leaks out
2. The passive refrigerant leak is a type of leak the intermittently occurs. They are really hard to find, because technicians should recreate the same conditions of pressure, temperature or vibration for the leak to happen.