Controls and Compressor Operation
WARNING: This page is about a different car, the 2016 Ford Transit Connect. However, it is still accessible from the selected car via links, so may be relevant.
All customer commands for the EMTC climate control system come through the HVAC control head.
A/C Request
When the A/C button is pressed, the HVAC control module uses a dedicated wire to send the A/C request message 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 is not excessively high or low.
- the engine coolant temperature is not excessively high.
- the ambient air temperature is above approximately 0 °C (32 °F).
- a WOT condition is not present.
- the evaporator discharge air temperature is above approximately 1 °C (33.8 °F).
Compressor Clutch
When A/C is requested and A/C line pressures allow, a ground is provided to the A/C clutch relay coil from the PCM, energizing the A/C clutch relay. When the PCM energizes the relay, voltage is supplied to the A/C compressor clutch field coil from the relay.