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Home >> Jeep >> 2023 >> Wagoneer Carbide, RWD >> Repair and Diagnosis >> Heating, Ventilation & A/C (HVAC) >> HVAC Control Systems >> Heating And Air Conditioning (ATC) - DTCS B1053-96 To B10C4-11 >> DTC Troubleshooting >> B1059-4B-3RD Row Mode Door 1 Control-Over Temperature >> Theory Of Operation

Theory Of Operation

The Mode and Temperature (Blend) Doors are opened and closed with electric actuators that provide a position signal. There are five circuits that run between each actuator and the HVAC Module:

The position signal is used by the HVAC module to monitor the door position. If the desired positions cannot be reached during normal operation, a DTC will set. All of the circuits are also monitored, either directly or indirectly, for open/short circuit faults.



This vehicle uses four actuators in the front HVAC system to adjust the temperature in the two zones within the passenger compartment. The front HVAC module also controls the rear HVAC system mode door actuators with a LIN bus.

The door actuators are direct current motors controlled at 12 volts, but usually operate between 9 and 16 volts. The HVAC housing contains two front blend door actuators, one mode door actuator, and one recirculation door actuator. All front actuators operate in the same fashion.

The actuators work in conjunction to control both the temperature of the air being distributed and the volume of the air flowing throughout the vehicle. The temperature is controlled directly using the temperature blend doors, however, the volume of air flow is achieved using the mode doors to close off the direction of the air flow, thus restricting the amount of air allowed to pass that particular door. This allows air flow from a single blower motor to be used for the entire vehicle yet gives individual control of the air volume to each front seat occupant and a rear seat occupant.

The specific feature of the potentiometer is that it is linear. The potentiometer receives a 12 volt power supply at terminal 4 and receives a ground at terminal 1. The LIN input to each actuator is at terminal 2 and exits to the next actuator at terminal 3 on all actuators except the last actuator in the system.

Two types of actuator are used in the HVAC system; 4-wire LIN actuators and 5-wire hard wired actuators. Each of the rear mode door actuators are connected via a LIN bus to the front HVAC module and are controlled by the front HVAC module. The blend door actuator(s), one in the Tri-Zone system or two in the Quad-Zone system, are hard wired to the rear HVAC module and are controlled by the rear HVAC module. The front and rear HVAC modules communicate with each other to determine the proper positioning of the rear mode door actuators.

All actuators are direct current motors controlled at 12 volts, but usually operate between 10 volts and 16 volts.

The specific feature of the blend door actuator potentiometer is that it is linear. The potentiometer receives a 5 volt power supply at terminal 3 and receives the ground at terminal 1. The signal of the potentiometer exits terminal 2 and is compared with the supply of the HVAC module. This is not an absolute value, it is a percentage of the power supply. Therefore this measurement is not linked to the level of the battery. The value of the potentiometer resistance must be about 4.7 kilohms.

For additional information regarding the description and operation of the HVAC system. Refer to HVAC SYSTEM, DESCRIPTION AND OPERATION .

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