A/C Signal: Description and Operation
PURPOSE/OPERATIONWhen the driver turns on the A/C system, a positive Voltage signal is supplied to the PCM (as an indication that the A/C system is needed) and to one side of the A/C relay coil, located on the LH inner fender panel. The PCM determines if engine conditions are suitable for A/C operation (engine temperature, idle speed, ignition timing and air/fuel mixture). If the the engine coolant temperature switch is closed (temp. below 235° F) the A/C ON signal is transmitted to the PCM. If the PCM senses that conditions are suitable for A/C operation, it supplies the ground circuit for the A/C relay coil, energizing it. This allows the relay to supply Voltage to the compressor clutch.