Test Description
WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.
The numbers below refer to the step numbers on the diagnostic table.
- 2: This step checks for continuous operation of the blower motor.
- 3: The test lamp should not illuminate while connected to any of the blower motor control circuits when the blower motor switch is in the OFF position. Illumination of the test lamp during this step indicates a malfunctioning blower motor switch or a short to voltage on a blower motor control circuit.
- 4: Test the blower motor control circuit that illuminated the test lamp in Step 3.
Blower Motor Always On
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor is ON while the blower motor switch is in the OFF position. |
|||
| 1 | Did you perform the HVAC diagnostic system check? | Go to Step 2 | Go to Diagnostic System Check - HVAC Systems - Manual |
| 2 |
|
Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 |
IMPORTANT:
The blower motor switch must remain in the OFF position during this step.
|
Go to Step 4 | Go to Step 5 |
| 4 | Test the appropriate blower motor control circuit for a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 10 | Go to Step 7 |
| 5 | Visually inspect the blower motor supply voltage circuit of the blower motor harness for a short to voltage with the vehicle harness. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 10 | Go to Step 6 |
| 6 | Inspect for poor connections at the harness connectors of the blower motor resistor assembly. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 10 | Go to Step 8 |
| 7 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
Go to Step 10 | Go to Step 9 |
| 8 | Replace the blower motor resistor. Refer to Blower Motor Resistor Replacement
in Heating, Ventilation and Air Conditioning. Did you complete the replacement? |
Go to Step 10 | - |
| 9 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? |
Go to Step 10 | - |
| 10 | Operate the system in order to verify the repair. Did you correct the condition? |
System OK | Go to Step 2 |