How to Test a Fan Clutch

What You'll Need
Car keys
Rolled up newspaper or yardstick

The fan clutch is an important part of your vehicle's engine cooling system. The fan clutch is a thermostatic control that operates the radiator fan independent of engine speed. It increases or decreases airflow over the radiator depending on how much cooling is needed. If your fan clutch fails to engage, the engine can overheat. If the clutch never releases, gas mileage will drop.

Step 1 - Start Car

Start a cold engine with the hood up, and visually confirm that the radiator fan is turning. Push the accelerator pedal to rev the engine. The fan speed should increase with engine speed at this point. If not, replace the clutch.

Step 2 - Allow Engine to Stabilize

After five minutes, the operating temperature should stabilize around 200 degrees F and fan should slow down. If the fan doesn't slow, the clutch may be siezed. If the coolant temperature continues to rise, the clutch may not engage.

Step 3 - Attempt to Turn Fan

Shut off engine. Attempt to turn fan. If it does not turn or turns with no resistance, then the fan clutch is faulty and needs replaced.