Test Description
The number(s) below refer to the step number(s) on the diagnostic table.
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This step will determine if one or more blower speeds are inoperative.
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This step determines if the HVAC control module and blower motor control processor are attempting to control the blower motor speed.
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The measured voltage on the blower speed control circuit should steadily decrease from 4.60 volts to 1.1 volts as the blower speed is adjusted from the minimum speed position to the maximum speed position.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics DEFINITION: The blower motor operates in at least one, but not all, speed positions. | ||||
1 | Did you perform the HVAC Diagnostic System Check? | -- | Go to Step 2 | |
Does the blower motor operate at the desired speed(s)? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
3 |
Does scan tool indicate that the Desired Blower Mtr Speed parameter continuously increases within the specified range? | 15-111 counts | Go to Step 4 | Go to Step 10 |
Does the test lamp illuminate and increase intensity? | -- | Go to Step 8 | Go to Step 5 | |
5 | Test the battery positive voltage circuit and ground circuit of the blower motor control processor for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 14 | Go to Step 6 |
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Important: Ensure that the blower motor control processor and HVAC control module connectors are connected during this step in order to avoid misdiagnosis.
Does the measured voltage continuously decrease between the specified values? | 4.7-1.0 V | Go to Step 9 | Go to Step 7 | |
7 |
Does the voltage measure near the specified value? | 5.0 V | Go to Step 10 | Go to Step 9 |
8 | Inspect for poor connections at the harness connector of the blower motor. 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 14 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of the blower motor control processor. 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 14 | 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 14 | Go to Step 13 |
11 | Replace the blower motor. Refer to Blower Motor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 14 | -- |
12 | Replace the blower motor control processor. Refer to Blower Motor Control Processor Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
13 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | -- | Go to Step 14 | -- |
14 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 |
