Radiator Cooling Fan: Testing and Inspection

DIESEL

NOISE

NOTE: It is normal for fan noise to be louder (roaring) when:

- Fan duty cycle high. This may occur when ambient (outside air temperature) is very high.
- Engine loads and temperatures are high such as when towing a trailer.
- Operating conditions where transmission temperatures may be high
- Cool silicone fluid within the fan drive unit is being redistributed back to its normal disengaged (warm) position. This can occur during the first 15 seconds to one minute after engine start-up on a cold engine.

LEAKS

Viscous fan drive operation is not affected by small oil stains near the drive bearing. If leakage appears excessive, replace the fan drive unit.

ELECTRONICALLY CONTROLLED VISCOUS DRIVE - DIESEL





If the fan assembly does not free-wheel and a metallic grinding sound exists, replace the electronically controlled fan drive.

NOTE: The following test may take up to 15 minutes to perform.

The engine should be at normal operating temperature.

1. Set the parking brake and verify the transmission is in park or neutral.
2. Set air conditioner (if equipped) and blower fan to OFF.
3. Start and allow engine to reach normal operating temperatures.
4. Stop engine, connect the scan tool and select appropriate model year and engine option.
5. Check for and correct existing DTC's
6. Using Tool 6801, backprobe pin 1 of the electronically controlled viscous fan drive connector, with the harness connected located at the lower fan shroud to battery ground.

NOTE: The fan drive control coil is energized to 12 volts at this time.

WARNING: A spark may occur when connecting pin to ground. Be sure that no combustible material is in the area.

7. Using the scan tool, verify that DTC 0480 set. If it is not set, verify that a good ground is available.
8. Start the engine.
9. Actuate engine speed to 2000 RPM.
10. Go to the SENSOR screen and observe the fan speed.
11. Run the engine at 2000 RPM until the fan speed increases to 1850 RPM or more for 30 seconds.

NOTE: Fan RPM may ramp up slowly.

NOTE: It maybe take 15 minutes before fan speed increases.

12. The fan speed should be in accordance to the table below.
13. If fan speed does not increase, make sure that the jumper wire has a good connection. If so replace the electronically control viscous fan drive.
14. If the fan speed does increase and there is still a concern, refer to the appropriate Engine Electrical Diagnosis to diagnosis the electronically controlled viscous fan drive control circuit.

CAUTION: If the viscous fan drive is replaced because of mechanical damage, the cooling fan blades should also be inspected. Inspect for fatigue cracks or chips that could result in excessive vibration. Replace fan blade assembly if any of these conditions are found.

Electronically Controlled Viscous Fan Drive Speeds: