Test Description
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A short to ground in the positive voltage circuit of the blower motor will cause the HVAC BLO fuse to open when high speed (position 5) is requested. It will also cause the thermal protection to open in the blower motor control resistor when low (position 1) or medium (position 2, 3, and 4) speed is requested.
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This step tests for a short to ground in the blower motor switch circuits. A short to ground in a speed control circuit will cause the A/C BLOWER fuse to open when that speed is selected.
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If the test lamp illuminates in all positions, the ignition positive voltage circuit of the blower motor switch is shorted to ground.
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This step tests for a high resistance or an open in the ignition positive voltage circuit of the blower motor switch.
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This step tests for a high resistance or an open in the ground circuit of the blower motor resistor.
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This step tests for a high resistance or an open in the positive voltage circuit of the blower motor.
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This step tests for a high resistance or an open in the ground circuit of the blower motor.
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A short to ground in the OFF speed control circuit will cause the A/C BLO fuse to open when the blower motor is turned off.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you review the Control Assembly Description and perform the necessary inspections? | -- | Go to Step 2 | Go to Symptoms |
2 |
Does the blower motor operate in all speeds? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
3 | Does the blower motor operate in any speed? | -- | Go to Symptoms | Go to Step 4 |
4 | Inspect the A/C FAN fuse. Is the fuse open? | -- | Go to Step 6 | Go to Step 5 |
Inspect the HVAC BLO fuse. Is the fuse open? | -- | Go to Step 14 | Go to Step 8 | |
Does the test lamp illuminate in any position? | -- | Go to Step 7 | Go to Step 13 | |
Does the test lamp illuminate in all positions? | -- | Go to Step 17 | Go to Step 18 | |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 12 | |
Probe the low (1) speed control circuit with a test lamp that is connected to the ground circuit of the blower motor resistor. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 19 | |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 14 | |
Probe the positive voltage circuit of the blower motor with a test lamp that is connected to the ground circuit of the blower motor. Does the test lamp illuminate? | -- | Go to Step 16 | Go to Step 14 | |
12 | Test the ignition positive voltage circuit of the blower motor switch for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 15 |
Test the OFF speed control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 14 | |
14 | Inspect for poor connections at the harness connector of the blower motor resistor. 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 23 | Go to Step 20 |
15 | Inspect for poor connections at the harness connector of the blower motor switch. 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 23 | Go to Step 21 |
16 | 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 23 | Go to Step 22 |
17 | Repair the short to ground in the ignition positive voltage circuit of the blower motor switch. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | -- |
18 | Repair the short to ground in the suspect speed control circuit (1, 2, 3, 4, or 5) that illuminated the test lamp. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | -- |
19 | Repair the high resistance or the open in the ground circuit of the blower motor resistor. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 23 | -- |
20 | Replace the blower motor resistor. Refer to Blower Motor Resistor Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- |
21 | Replace the heater - A/C control. Refer to Control Assembly Replacement . Did you complete the replacement? | -- | Go to Step 23 | -- |
22 | Replace the blower motor. Refer to Blower Motor and Fan Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 23 | -- |
23 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 2 |
