How do you test to see if a fan clutch is working properly. I am not having any cooling problems, but I don't know how they normally fail. Does the clutch seize? Which would just have the fan moving full speed all the time.

I would love some experienced thoughts on how to test?

thanks,

 

Fan Clutch Diagnostic Procedure

1. NOISE
Fan noise is sometimes evident under the following normal conditions:
a. when clutch is engaged for maximum cooling.
b. During first few minutes after start-up until the clutch can re-distribute the silicone fluid back to its normal disengaged operating condition after overnight settling.
However, fan noise or an excessive roar will generally occur continuously under all high engine speed conditions (2500 rpm and up) if the clutch assembly is locked up due to an internal failure. If the fan cannot be rotated by hand or there is a rough grating feel as the fan is turned, the clutch should be replaced.

2. LOOSENESS
Under various temperature conditions, there is visible lateral movement that can be observed at the tip of the fan blade. This is a normal condition due to the type of bearing used. Approximately 1/4" maximum lateral movement measured at the fan tip is allowable. This is not cause for replacement.

3. SILICONE FLUID LEAK
The operation of the unit is generally not affected by small fluid leaks which may occur in the area around the bearing assembly. However, if the degree of leakage appears excessive, proceed to item 4.

4. ENGINE OVERHEATING
a. Start with a cool engine to insure complete fan clutch disengagement.
Refer to Item 1, paragraph 1.
b. If the fan and clutch assembly freewheels with no drag (revolves over 5 times when spun by hand), the clutch should be replaced. If clutch performs properly with a slight drag, go to step c.
Testing a fan clutch by holding the small hub with one hand and rotating the aluminum housing in a clockwise/counterclockwise motion will cause the clutch to freewheel, which is a normal condition when operated in this manner. This should not be considered a test by which replacement is determined.
c. Use dial-type thermometer J 23640, or similar type. J 23640 reads to 115C (220F), therefore, allow approximately 3/16" pointer movement for each 6C (10F) over 82C (180F).
Position thermometer so that the thermometer sensor is centered in the space between the fan blades and radiator. This can be achieved by inserting the sensor through one of the existing holes in the fan shroud or fan guard, or by placing between the radiator and the shroud. On some models, it may be necessary to drill a 5mm 3/16" hole in the fan shroud ti insert J6742-01.

NOTICE: Check for adequate clearance between fan blades and thermometer sensor before starting engine.

d. Cover radiator grille sufficiently to induce a high engine temperature. Start engine and turn on A/C if equipped. Maintain a position in front of the vehicle to observe the thermometer reading while engine is running at approximately 2000 rpmn. Use tachometer if available.
e. Observe thermometer reading when clutch engages. It will take approximately 5 to 10 minutes for the temperature to become high enough to allow engagement of the fan clutch. This will be indicated by an increase or roar in fan air noise and by a drop in the thermometer reading of approximately 3-8C (5-15F). If the clutch did not engage between 65-88C (150-190F), the unit should be replaced.
Be sure fan clutch was disengaged at beginning of test.
If no sharp increase in fan noise or temperature drop was observed and the fan noise level was constantly high from start of test to 88C (190F), the unit should be replaced.

NOTICE: Do not continue test past a thermometer reading of 88C (190F) to prevent engine overheating.

f. As soon as the clutch engages, remove the radiator grille cover and turn off the A/C to assist in engine cooling. The engine should be run at approximately 1500 rpm.
g. After several minutes the fan clutch should disengage, as indicated by a reduction in fan speed and roar.

 

Thanks a million!!!