A/C Signal: Description and Operation

The fuel control unit is signaled by the A/C control unit whenever the A/C is turned on. The fuel control unit then responds by modifying the duty cycle to the idle stabilizer valve, increasing the idle speed by approximately 100 rpm. This is to ensure a smooth idle with the additional load of the A/C compressor, as well as to ensure more efficient A/C operation when the engine is idling.