Control Components: EMTC

WARNING: This page is about a different car, the 2016 Ford Taurus. However, it is still accessible from the selected car via links, so may be relevant.

The EMTC components are used to select:

air inlet source (outside or recirculated).
blower motor speed.
discharge air temperature (temperature blend).
discharge air location (defrost, panel, floor).
A/C compressor operation.

Control System Inputs

HVAC Control Module

The EMTC system uses a remote HVAC control module that is separate from the control interface.

The FCIM provides the interface for the vehicle occupants to control the climate control system. When selections are made, the FCIM communicates the selections to the HVAC control module through the vehicle module communication network. The remote HVAC control module controls the climate control system based on the FCIM selections.

In-Vehicle Temperature and Humidity Sensor

The in-vehicle temperature and humidity sensor contains 2 thermistors which separately measure the in-vehicle air temperature and humidity and send those readings to the HVAC control module. The in-vehicle temperature and humidity sensor has an electric fan within the sensor that draws in-vehicle air across the thermistors.

AAT Sensor

The AAT sensor signal is received by the HVAC control module over the vehicle module communication network from the PCM.

For information regarding the outside air temperature display, refer to Instrumentation, Message Center, and Warning Chimes .

Control System Outputs

The EMTC system has 4 system outputs.

Blower Motor Speed Control

The HVAC control module controls the blower speed by sending a PWM signal to the blower motor speed control. The blower motor speed control provides variable ground feed for the blower motor to control the speed. A delay function provides a gradual increase or decrease in blower motor speed under all conditions.

The blower motor speed control has internal temperature and surge protection. In the event of excessive blower motor supply voltage or current draw, or if the blower motor speed control temperature climbs considerably due to a failure event (such as a seized or partially-seized blower motor), the blower motor speed control automatically shuts down the blower motor. After shutdown, the blower motor speed control attempts to restart every 120 seconds until the blower motor can be safely operated.

Temperature Blend Door Position

The temperature blend door actuator moves the temperature blend door on command from the HVAC control module.

The temperature blend door actuator contains 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 circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC control module from the contact wiper indicates the position of the temperature blend door. The HVAC control module powers the actuator motor to move the temperature blend door to the desired position selected by the vehicle occupants.

Defrost/Panel/Floor Mode Door Position

Airflow through the HVAC plenum is controlled by the defrost/panel/floor mode door actuator. The defrost/panel/floor mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC control module to monitor the position of the defrost/panel/floor mode door. 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 circuit is connected to a contact wiper, which is driven along the variable resistor by the actuator shaft. The signal to the HVAC control module from the contact wiper indicates the position of the defrost/panel/floor mode door. The HVAC control module powers the actuator motor to move the defrost/panel/floor mode door to the desired position selected by the vehicle occupants.

Air Inlet Mode Door Position

The air inlet mode door actuator contains a reversible electric motor and potentiometer. The potentiometer allows the HVAC control module to monitor the position of the air inlet mode door. The HVAC control module adjusts the air inlet door depending on the humidity measured by the in-vehicle temperature and humidity sensor. If the vehicle cabin becomes too humid and recirculated air is not selected, the HVAC control module adjusts the air inlet door to allow more recirculated air. When the humidity level drops, it adjusts back to fresh air.