Air Conditioning Switch: Description and Operation

When the A/C switch "ON" signal is received by the ECU, it signals the idle speed control (ISC) valve to increase the amount of bypass air, raising the idle speed. This ensures stable idling by compensating for extra engine load created by the A/C compressor.

The ECU energizes the A/C relay to engage the compressor clutch when it receives an "ON" signal from the A/C switch. Concurrently, the ECU makes adjustments to fuel injection quantity, idle speed and ignition timing to maintain smooth engine operation.