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.