Toyota
Dodge Durango
 Service Manual
Heating and Air Conditioning » Diagnosis and testing
Heater-a/c control

Satisfactory heater and air conditioner performance depends upon proper operation and adjustment of all operating controls and refrigeration system components. For circuit descriptions and diagrams, refer to 8W-42 - Air Conditioning/Heater in Group 8W - Wiring Diagrams. These inspections, tests, and adjustments should be used to locate the cause of a malfunction.

Operation must be tested as described in the following sequence: (1) Move the temperature control knob quickly to the full hot and the full cold positions. There should be a distinct sound of the blend-air door hitting its stops within the heater-A/C housing at the end of  knob travel in each direction, with no spring-back of the knob. If not OK, inspect the condition, routing, installation and adjustment of the temperature control cable. See Temperature Control Cable in the Removal and Installation section and in the Adjustments section of this group for more information.

(2) Inspect and adjust the serpentine drive belt.

Refer to Group 7 - Cooling System for the procedures.

(3) Start the engine and hold the idle speed at 1,300 rpm.

(4) On vehicles with air conditioning, turn the temperature control knob to the extreme counterclockwise (Cool) position, and set the mode control switch knob in the Bi-Level (A/C) position. The outside (recirculation) air door should be open to outside air. If not OK, see Vacuum System in the Diagnosis and Testing section of this group.

(5) Open the vehicle windows. Test the blower motor operation in all speeds. If not OK, see Blower Motor in the Diagnosis and Testing section of this group. Leave the blower motor switch knob in the highest speed position.

(6) On vehicles with air conditioning, the compressor should be running and the air conditioning system in operation unless the ambient air temperature is below about -1 C (30 F). If not OK, see A/C Performance in the Diagnosis and Testing section of this group.

(7) Check the mode control switch operation. The heater and air conditioner systems should respond as described in the owner's manual in the vehicle glove box to each mode selected. Reduce the engine speed to normal idle. The vacuum will be high at low idle and the vacuum actuators should respond quickly. If not OK, see Vacuum System in the Diagnosis and Testing section of this group.

(8) If the vacuum tests, and the electrical component and circuit tests reveal no problems, disassemble the heater-A/C housing to inspect for mechanical misalignment or binding of the mode doors.

    More about «Diagnosis and testing»:

    A/c performance

    Blower motor

    Blower motor relay

    Blower motor resistor

    Blower motor switch

    Compressor

    Compressor clutch coil

    Electronic cycling clutch switch (front unit only)

    Heater-a/c control

    Heater performance

    Dual function high pressure switch/high pressure cut-off switch

    Low pressure cut-off switch

    Refrigerant system leaks

    Refrigerant system service equipment

    Vacuum system

    Dodge Durango Service Manual / Heating and Air Conditioning / Diagnosis and testing / Heater-a/c control

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