How to test fan clutch?

[BDaugherty]

Can anyone tell me the correct operation of the fan clutch on my 2003 HO truck? Also, what is the procedure to test it.



I have a situation where sometimes the fan clutch is engaged after a cold start and it doesn't release for the first mile or so. I'm also concerned that if it is engaged during cranking, it might contribute to my no start cold condition by causing reduced cranking speed and trouble building rail pressure. See my other post on that matter:

https://www.turbodieselregister.com...003-2007/234995-how-test-injector-return.html

 

[Bob4x4]

Is that with the defroster on? The fan is software controlled. Since it is monitored it will also set dtc's. The Ecm knows it's rpm.

 

[Bob4x4]

ELECTRONICALLY CONTROLLED VISCOUS FAN DRIVE

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.

Aggressive engine braking down a steep grade 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

If the fan assembly free-wheels without drag (the fan blades will revolve more than five turns when spun by hand), do not replace the fan drive. This spin test must be performed when the engine is cool.



If the fan assembly does not free-wheel and a metallic grinding sound exists, replace the electronically controlled fan drive (Refer to 7 - COOLING/ENGINE/RADIATOR FAN - REMOVAL).



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



The engine should be at normal operating temperature.



Set the parking brake and verify the transmission is in park or neutral.

Set air conditioner (if equipped) and blower fan to OFF.

Start and allow engine to reach normal operating temperatures.

Stop engine, connect the DRB III and select appropriate model year and engine option.

Check for and correct existing DTC's

Using Tool 6801, connect pin 1 of the electronically controlled viscous fan drive connector, located at the lower fan shroud to battery ground (Electronically Controlled Viscous Fan Drive Connector).

Using the DRB III, verify that DTC 0480 set.

Start the engine.

Go to the SENSOR screen and observe the fan speed.

Run the engine at 2500 rpm.

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



The fan speed should increase according to the table below.

If fan speed does not increase, replace the electronically control viscous fan drive. ELECTRONICALLY CONTROLLED VISCOUS FAN DRIVE SPEEDS

ENGINE RPM FAN RPM (Min)

500 490

1000 950

1500 1420

2000 1850

2500 2230

3000 2440





If the fan speed does increase and there is still a concern, refer to the appropriate Powertrain Diagnosis Manual 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.

 

[BDaugherty]

Thanks, Bob4x4. The fan noise during the first minute of operation after cold start sounds like what I have, however my fan will not free spin on a cold engine. It has viscous resistance such that it will not spin 1 full revolution when spun by hand. There is no bearing noise. What do you think about that?

 

[Bob4x4]

I wouldn't worry about it,we have had flashes that change when and how the fan comes on. Our durangos worked the same way,very loud and spun when cold for about a minute or 2.