How to Test a Fan Clutch
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 frozen. If the coolant temperature continues to rise, the clutch may not engage.
Step 3 - Attempt to Obstruct Fan
The last test is to try and stop the rotation of the engine fan. Wear safety glasses during this test. Push a rolled up paper or stick against the hub of the fan. If it stops easily, the clutch is in poor condition.