The A/C pressure sensor is attached to a receiver pipe of the A/C condenser exit side. This sensor uses the sensor that the output voltage changes by the pressure. The PCM receives the signal and is used to drive the A/C compressor. The PCM also controls the radiator fan and A/C condenser fan. When the A/C system pressure rises than an upper limit, or decreases than a lower limit, the PCM stops the A/C compressor to protect the system.