The HVAC control assembly applies voltage to the blower motor control circuit that corresponds to the selected blower speed. The resistors and the blower motor are in a series circuit. The following list represents the number of resistors in series with the blower motor per particular speed request:

When the operator requests High speed, the HVAC control assembly applies voltage to the blower motor through the high blower motor relay.

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

Ignition ON, mode selector set to Panel, cycle the blower motor from LOW to HIGH using the blower motor switch. The blower motor should operate in each speed position.

1. Ignition OFF, disconnect the X2 harness connector at the HVAC control assembly.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal E and ground.

⇒	If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance.

3. Ignition OFF, connect the X2 harness connector at the HVAC control assembly. Disconnect the X1 harness connector at the HVAC control assembly.
4. Ignition ON, cycle the mode selector through each position. Verify a test lamp illuminates between the control circuit terminal A in each mode position.

⇒	If the test lamp does not illuminate in each position, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control assembly.

5. Ignition OFF, connect the X1 harness connector at the HVAC control assembly. Disconnect the harness connector at the blower motor resistor assembly.
6. Test for less than 5 ohms between the ground circuit terminal C and ground.

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

7. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal A and ground.

⇒	If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.

8. Mode selector set to Panel, while changing the fan speed switch between LOW, M1, M2 and HIGH, verify that a test lamp illuminates between the appropriate control circuit terminals listed below and ground:

•	LOW - terminal E

•	M1 - terminal D

•	M2 - terminal F

•	HIGH - terminal B

⇒	If the test lamp does not illuminate, test the appropriate control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control assembly.

9. Ignition OFF, connect the harness connector at the blower motor resistor assembly. Disconnect the harness connector at the blower motor.
10. Test for less than 5 ohms between the ground circuit terminal A and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the blower motor resistor assembly.

11. Ignition ON, mode selector set to Panel, connect a test lamp between the control circuit terminal B and ground circuit terminal A.
12. Cycle the fan speed switch between LOW, M1, M2 and HIGH speeds. The test lamp should illuminate and change in intensity as the blower speed is varied.

⇒	If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the blower motor resistor assembly.

⇒	If the test lamp illuminates but does not change intensity, test the control circuit for a short to voltage. If the circuit tests normal, replace the blower motor resistor assembly.

13. If all circuits test normal, test or replace the blower motor.

1. Ignition OFF, disconnect the harness connector at the blower motor.
2. Install a 40-amp fused jumper wire between the control circuit terminal B and 12 volts. Install a jumper wire between the ground circuit terminal A and ground. Verify the blower motor activates.

⇒	If the blower motor does not activate, replace the blower motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.