Circuit Operation

When the A/C-heater control switch is moved to an A/C position or the defrost position, it connects circuit C90 to ground on circuit Z8. Circuit C90 connects to cavity C23 of the Powertrain Control Module (PCM). When circuit C90 connects to ground circuit Z8, it provides the A/C select signal to the PCM.

When the A/C high pressure and low pressure switches are closed, circuit C90 connects to circuit C21, and circuit C21 connects to circuit C22. Circuit C22 connects to cavity C22 of the PCM. The PCM senses the A/C request signal on circuit C22 when the A/C-heater control switch is in defrost or an A/C position.

After sensing the A/C request signal, the PCM supplies ground for the coil side of A/C compressor clutch relay on circuit C13. Circuit C13 originates at cavity C1 of the PCM. Circuit F12 from fuse 11 in the fuse block powers the coil side of the A/C compressor clutch relay.

When the PCM grounds the A/C compressor clutch relay the contacts close and connect circuit A17 from fuse 9 in the Power Distribution Center (PDC) to circuit C3. Circuit C3 supplies power to the case grounded A/C compressor clutch.

The A/C compressor clutch has a built-in diode. The diode controls the induced voltage that results from the magnetic field collapsing when the clutch disengages. The diode provides a current path to protect other components and systems.