A/C On (A/C Request) Signal

The air conditioner "on" switch is mounted in instrument panel. This 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 air conditioner compressor clutch is engaged. On some models, ECM may also activate radiator cooling fan when this signal is present. If this signal is not present on A/C equipped vehicles, vehicle may idle rough when A/C compressor cycles. To check function of the A/C switch, perform functional check of switch. See I - SYS/COMP TESTS article in this section.