Description
PCM receives an A/C request signal from Instrument Panel Cluster (IPC) over serial data line. When A/C is requested, PCM provides a ground path to A/C clutch relay control circuit. When relay circuit is grounded, A/C clutch relay is energized. After A/C request has been selected, PCM will delay grounding A/C clutch relay control circuit for .3 second. This allows PCM to adjust engine idle RPM for additional load.
PCM will temporarily de-energize A/C clutch relay for a hot engine restart, during wide open throttle, when engine speed is greater than 6000 RPM, or during Idle Air Control (IAC) valve reset. A/C clutch relay will remain de-energized when DTC P0530 is set, or if there is no A/C request signal due to an open A/C select switch circuit.
Vehicle Control Module (VCM) controls compressor clutch to improve idle quality and performance by delaying compressor clutch engagement until idle speed is increased, releasing compressor clutch when idle speed is too low, and smooths cycling of compressor clutch by providing additional fuel the instant compressor clutch is applied.
Turning on A/C supplies battery voltage through pressure switches to VCM. When VCM receives voltage on A/C request signal, A/C clutch relay circuit is grounded. As a result, compressor clutch engages.