Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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This step tests for blower motor operation in any speed setting.
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This step identifies if the HVAC control module is commanding the blower motor to operate at HI speed.
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This step verifies that power is being supplied to the blower motor.
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This step tests for a possible open in the blower motor ground circuit or a bad motor.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Blower Control Schematics | ||||
1 | Did you review the HVAC operation and perform the necessary inspections? | -- | Go to Step 2 | Go to Diagnostic System Check |
Does the blower motor operate in each speed position? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
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Important: Place the HVAC control module blower switch in the max. speed position. Place the MODE selector in any position except AUTO. This will ensure a full speed condition when the blower motor is commanded to an ON position. Failure to do this may result in a misdiagnosis.
Is the blower motor PWM parameter at the specified value? | 98% | Go to Step 4 | Go to Step 10 | |
4 | With a volt meter measure the voltage on the blower motor control circuit while rotating the blower motor switch from min. to max. position. Does the voltage vary between the specified value? | 4.0-0.4 Volts | Go to Step 5 | Go to Step 9 |
Does the test lamp illuminate and change intensity? | -- | Go to Step 6 | Go to Step 8 | |
Does the test lamp illuminate and change intensity? | -- | Go to Step 14 | Go to Step 7 | |
7 | Test the blower motor control module ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 11 |
8 | Test the blower motor control module battery positive voltage circuit for an open or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 10 |
9 | Test the blower motor control module control circuit for a high resistance, open or. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 12 |
10 | 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 15 | Go to Step 13 |
11 | Inspect for poor connections at the harness connector of the blower motor 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 15 | Go to Step 14 |
12 | Replace the HVAC control module. Refer to Control Assembly Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 15 | -- |
13 | Replace the blower motor control module. Did you complete the replacement? | -- | Go to Step 15 | -- |
14 | Replace blower motor. Refer to Blower Motor and Fan Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 16 | -- |
15 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 |
