A/C Signal: Description and Operation

Circuit Description:
The A/C solenoid vacuum (SV) valve is located in the center engine compartment mounted to the bulkhead. When the A/C switch is turned ON, the A/C amplifier sends the engine control module (ECM)/powertrain control module (PCM) an A/C ON signal. The ECM/PCM grounds the A/C SV valve, allowing additional air to enter the intake manifold. As a result of the increased air in he intake manifold, the engine idle speed is increased. The ECM/PCM sends the A/C amplifier an A/C cutout signal during certain heavy engine loads conditions. When the A/C amplifier receives this signal from the ECM/PCM, it immediately cuts out A/C compressor operation. When the engine returns to a lighter load, the ECM/PCM negates the A/C cutout signal. At this point, the A/C amplifier can resume normal cycling of the A/C compressor clutch.