A/C On/Request Signal

The A/C power switch provides a simple "on" (A/C request) signal, which is monitored by the ECM. The ECM uses this signal to determine control of the A/C clutch relay (if equipped) and to adjust idle speed when A/C compressor clutch is engaged. ECM activates radiator cooling fan when this signal is present. If this signal is not present, vehicle may idle rough when A/C compressor cycles.