Head Relief Function

Prior to every activation of the compressor motor, the height sensor closes switch A and C, energizing the exhaust solenoid for approximately 1 second to relieve the pressure in the compressor head. This prevents the compressor from trying to start against a high head pressure, drawing a high current, and potentially stalling and blowing the ALC fuse. This cycle is controlled by the height sensor and will not occur if the sensor is already in the exhaust mode (sensor arm below the in-trim zone).