When the optional air conditioning unit is installed, the idle speed must be increased when the air conditioner compressor is engaged. The compressor adds sufficient load to the engine that uneven idle or stalling may occur if compensation is not provided.
This system consists of a vacuum actuator and a vacuum solenoid valve. When the compressor is switched on, the solenoid valve is energized, allowing some vacuum from the power brake booster assembly to be bled into the actuator. As a result, the control lever is slightly pulled by the actuator, admitting more fuel to the engine. Consequently, the engine runs at a faster idle speed.