Mark a spot on the fan hub pulley and on one fan blade so the measuring device can determine the pulley and the fan speed. Reflective tape, Part Number 3377464, and optical tachometer, Part Number 3377462, can be used to mark the fan blade and the pulley.
While the engine is still at high idle, remove the radiator grill cover. The fan speed must begin to decrease after 1 minute and eventually drop to a maximum of 50 percent of the input pulley speed.
If the viscous fan hub does not pass this test, have it checked by an authorized fan hub dealer for repair or replacement.
If the fan does not operate within the temperature range indicated in the Thermal Control Settings Chart, as illustrated, the fan clutch and the controls must be checked. Refer to the OEM service manual.
If a fan speed measuring device is
not available and the complaint is overheating, remove the viscous fan hub bi-metal strip and the control pin. This will cause the fan hub to operate at all times.
If the overheating complaint does
not occur with the control pin removed, install the control pin and take the fan hub to an authorized fan hub dealer for repair or replacement.
Carefully remove the fan and clutch assembly from the fan shroud, and place it on a workbench with the pin side up.
Remove the capscrews or the hexagon nuts which hold the fan to the clutch.
NOTE: If the control pin is removed, the control pin side of the assembly must
be up to prevent fluid loss which will result in incorrect fan clutch performance.