Temperature Blend Door Position

WARNING: This page is about a different car, the 2008 Mercury Mariner and 2008 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.

The dual-zone EATC system uses 2 temperature blend door actuators to control 2 separate temperature blend doors. The temperature blend doors independently vary the LH side and RH side temperature settings, as desired. The temperature blend door actuators each contain a reversible electric motor and a potentiometer. The potentiometer circuit consists of a 5-volt reference signal connected to one end of a variable resistor, and a signal ground connected to the other. A signal return circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal returned to the HVAC module from the contact wiper indicates the position of the temperature blend door. The HVAC module drives the actuator motor in whichever direction is necessary to make the actuator contact wiper voltage agree with the expected HVAC module contact wiper voltage value, as determined by the control algorithm.

The temperature blend door actuators are mounted to the heater core and evaporator core housing.