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 PCM/VCM. The PCM/VCM 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. Control unit also activates 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 the SYSTEM/COMPONENT TESTS article.