A/C Signal: Description and Operation

The A/C signal in generated by the radiator fan control unit. The radiator fan control unit receives information from the A/C switch, a coolant temperature switch and a triple pressure switch. When system conditions (i.e. pressures and temperatures) are correct, the fan control unit sends a signal to the ECU requesting air conditioning. The ECU then grounds terminal B8 which closes the A/C clutch relay and allows the compressor to engage. Once the compressor is engaged, idle speed is raised through EACV control to compensate for the additional engine load.