A method and system for detecting a low charge condition in an air conditioner for a vehicle. The system first determines whether noise factors are present that would interfere with reliably measuring a pressure delta. If noise factors are not present, the system determines a pressure delta value for the compressor by comparing the high side pressure when the clutch is engaged to a high side pressure when the clutch is disengaged. If the pressure delta value is less than a threshold value, a low charge condition may be recorded. When the number of low charge conditions detected exceeds a predetermined number of events, the system may set a temperature diagnostic trouble code, disable the air conditioning system and alert the driver of a potential problem.