The auxiliary HVAC control assembly is an input to the primary HVAC control module. The primary HVAC control module uses a low reference circuit and a 5-volt reference circuit to determine the position of the auxiliary HVAC control switches. The auxiliary HVAC assembly has 3 signal circuits to relay the desired mode, temperature and blower motor speeds to the primary HVAC control module. The primary HVAC control module uses this input to adjust the desired positions of the mode, temperature and blower motor.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, verify DTC B0433 or B3782 is not set.

⇒	If either of the DTCs are set, refer to DTC B0228, B0413, B0423, B0433, B3779, or B3782 (RPO CJ2) or DTC B0228, B0413, B0433, B3779, or B3782 (RPO C67 or CJ3).

2. Individually adjust each of the controls on the auxiliary HVAC control assembly. Verify that the auxiliary blower motor, temperature actuator and Mode actuator move properly to the selected positions or desired speeds.

1. Ignition OFF, disconnect the harness connector at the auxiliary HVAC control assembly.
2. Ignition OFF, test for less than 1 ohm between the low reference circuit terminal 4 and ground.

⇒	If greater than the specified range , test the low reference circuit for an open/high resistance.

3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 3 and ground.

⇒	If greater than the specified range, test the 5-volt reference circuit for an short to voltage.

⇒	If less than the specified range, test the 5-volt reference circuit for an short to ground or an open/high resistance.

4. Ignition OFF, connect the harness connector at the auxiliary HVAC control assembly. Disconnect the X2 harness connector at the HVAC control module.
5. Ignition ON, verify voltage at the signal circuit terminal 19 varies between 0.5-4.5 volts while varying the auxiliary blower speed from low to high.

⇒	If not within the specified range, test the signal circuit for a short to voltage, a short to ground, or an open/high resistance. If the circuit tests normal, test or replace the auxiliary HVAC control assembly.

6. Verify voltage at the signal circuit terminal 8 varies between 0.5-4.5 volts while varying the auxiliary temperature setting from warm to cool.

⇒	If not within the specified range, test the signal circuit for a short to voltage, a short to ground, or an open/high resistance. If the circuit tests normal, test or replace the auxiliary HVAC control assembly.

7. Verify voltage at the signal circuit terminal 9 varies between 0.5-4.5 volts while selecting the three mode positions.

⇒	If not within the specified range, test the signal circuit for a short to voltage, a short to ground, or an open/high resistance. If the circuit tests normal, test or replace the auxiliary HVAC control assembly.

8. Ignition OFF, connect the X2 harness connector at the HVAC control module.
9. Ignition ON, verify the auxiliary blower motor speed changes while varying the blower speed setting on the auxiliary HVAC control assembly.

⇒	If the blower speed does not vary, refer to Auxiliary Blower Motor Malfunction (RPO CJ2) or Auxiliary Blower Motor Malfunction (RPO C67 or CJ3).

10. If all circuits test normal, replace the HVAC control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.