W 150 Pickup V6-239 39L (1991) AC Switch Description
Air Conditioning Switch: Description and Operation
When A/C is selected (turned ON) inside the vehicle, the A/C switch is ACTIVATED, which sends an input signal to the SBEC. When the SBEC
receives this input signal, it engages the compressor clutch by grounding the clutch relay. The engine controller maintains a specific rpm by controlling
the Idle Speed Control (ISC) actuator.
If the engine controller receives a signal from the A/C low pressure switch (indicating low Freon level), or the electric clutch cycling switch (indicating
evaporator freezing) the A/C relay will be DE-ENERGIZED to de-activate the A/C clutch.
