A/C Request

WARNING: This page is about a different car, the 2013 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

When the A/C is requested, the HVAC module sends the message over the MS-CAN to the BCM. The BCM sends the A/C request through the HS-CAN to the PCM.

When an A/C request is received by the PCM, the PCM engages the A/C clutch relay when:

the refrigerant pressure isn't excessively high or low.
the engine coolant temperature isn't excessively high.
the ambient air temperature is above 6 C (43 F).
a WOT condition is not present.
the evaporator discharge air temperature is above 7 C (45 F).