A/C Idle-Up Circuit

A/C amplifier sends an idle-up signal to PCM when A/C compressor clutch is in operation. PCM compensates for extra engine load by adjusting engine idle speed through IAC valve. See IDLE AIR CONTROL (IAC) VALVE. PCM then sends A/C amplifier an A/C cut-out signal to cut operation of A/C compressor clutch. A/C amplifier will then resume normal cycling of A/C compressor clutch when engine returns to a lighter load. A malfunction in A/C idle-up circuit can set Diagnostic Trouble Code (DTC) P0505. For testing procedures, see TESTS W/CODES article.