Climate Control System Logic

WARNING: This page is about a different car, the 2017 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The controls for the climate control system are offered in the location below:

DATC HVAC control module

On vehicles with SYNC ® system the touch screen does not offer climate control inputs.

On vehicles without touch screen, the customer preferences are input directly into the DATC HVAC control module.

Controls and Compressor Operation

Climate Control Commands - A/C Request

When the A/C is requested, the HVAC control 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 all of the following conditions are met:

The PCM does not detect excessively high or low refrigerant pressure from the A/C pressure transducer.
The PCM does not detect an ambient air temperature below approximately 0 °C (32 °F).
The PCM does not detect temperatures from the Mass Airflow/Intake Air Temperature sensor that does not correlate with other temperature sensor readings at ignition ON. (Most Mass Airflow (MAF) sensors have an integrated Intake Air Temperature (IAT) sensor).
The PCM does not detect a WOT condition.
The PCM does not receive a message from the HVAC control module detecting an evaporator temperature below approximately 1 °C (33.8 °F).

Compressor control and the evaporator temperature are a function of many parameters, not a straight on off to avoid freezing the evaporator. The PCM monitors multiple temperature sensors correlation (AAT, CHT, ECT IAT, MAF (as equipped)). The PCM runs this logic after an engine off and a calibrated soak period, typically 6 to 8 hours. This soak period allows the Ambient Air Temperature (AAT) sensor and the other temperature sensors to stabilize and not differ by greater than a calibrated value, typically 18 °C (32.4 °F). If a sensor input is found to be reporting a temperature imbalance the PCM does not allow the A/C clutch to engage. For more information on PCM sensors, Refer to Engine Controls - Introduction (Except Diesel & Hybrid) .