Circuit Description
The electro-viscous clutch is controlled by the powertrain control module (PCM). The PCM controls a solenoid that regulates a fluid pressure that controls slip of the fan clutch. Internal to the fan is a centrifugal fluid pump, solenoid, hall effect sensor, valve lever and hydraulic fluid. There are 2 chambers for the fluid. These 2 chambers are separated by a valve lever. The first chamber is the storage chamber, which holds excess fluid. The second chamber is the working chamber. As the pressure of the fluid is increased in the working chamber the amount of slip the fan has is decreased. The position of the valve lever is controlled by an electric solenoid.
Diagnostic Aids
| • | Turning off the engine when the cooling fan clutch is engaged, the cooling fan clutch will be engaged at engine restart. This may cause an excessive noise concern. This is a normal condition. |
| • | If the engine is turned off for an extended period of time, usually over night, the hydraulic fluid may fill working chamber and cause limited slip at engine restart. This may cause the excessive noise condition. This is a normal condition. |
| • | To engage the cooling fan clutch, it can take up to 2 minutes for a 100 percent command with the engine at 2,000 RPM. The lower the engine speed, the longer it will take the cooling fan clutch to engage. |
| • | To disengage the cooling fan clutch, it can take up to 2 minutes with the engine at 2,000 RPM. The lower the engine speed, the longer it will take to disengage. |
| • | In lower ambient air temperatures the cooling fan clutch will engage in less time, however it will take longer to disengage. |
| • | An inline connector could cause an intermittent DTC. Ensure to test for poor connections and pin retention at all inline connectors. Refer to system schematics for connector and locations. |
| • | If the condition is not present, refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems. |
Test Description
The numbers below refer to the step numbers in the diagnostic table.
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There should be no binding or increased resistance as the cooling fan clutch is rotated.
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The cooling fan noise should increase as the cooling fan clutch engages. It can take up to 2 minutes for full cooling fan clutch engagement. If cooling fan clutch is previously fully engaged, then there will not be a noticeable change in cooling fan noise. Compare noise to a known good vehicle. If fan noise is louder than the known good vehicle, then answer Yes.
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In the previous step the cooling fan clutch was fully engaged. This step tests to ensure that the cooling fan clutch will disengage. A noticeable noise difference should be heard between a fully engaged cooling fan clutch and a disengaged cooling fan. The cooling fan clutch is completely disengaged when the excessive fan noise is not heard.
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This step clears DTCs that were set during previous steps. Test driving the vehicle will attempt to set DTCs not previous found in the Engine Cooling Diagnostic Check. If no DTC is set, the condition is normal operation of the cooling fan.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Engine Cooling Schematics Connector End View Reference: Cooling System Connector End Views DEFINITION: The cooling fan clutch has excessive fan noise. | |||
1 | Did you perform the Engine Cooling Diagnostic System Check? | Go to Step 2 | |
Rotate the cooling fan 3 complete revolutions? Is the resistance of the cooling fan clutch even throughout each rotation? | Go to Step 4 | Go to Step 3 | |
3 | Inspect the cooling fan clutch for proper installation. Refer to Fan Clutch Replacement . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
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Important: DTC P1482, for 4.2L (LL8), and P0480, for 5.3L (LM4), will set when the cooling fan relay is disconnected.
Does the cooling fan clutch engage? | Go to Step 5 | Go to Step 8 | |
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Important: Continuous excessive fan noise is due to a mechanical failure. If the fan noise decreases during this step, then there is an electrical malfunction. Replacing the cooling fan clutch will not correct the condition.
Does the cooling fan disengage? | Go to Step 6 | Go to Step 11 | |
6 |
Are the high side pressure values within 138 kPa (20 psi) of each other? | Go to Step 7 | Go to Step 9 |
Does the scan tool display any cooling system DTCs? | System OK | ||
8 | Inspect for poor connections at the harness connector of the cooling fan clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
9 | Inspect for poor connections at the harness connector of the A/C high side pressure sensor. 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 12 | Go to Step 10 |
10 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning. Did you complete the replacement? | Go to Step 13 | -- |
11 | Replace the cooling fan clutch. Refer to Fan Clutch Replacement . Did you complete the replacement? | Go to Step 13 | -- |
12 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 8 |
13 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
