The Fan Clutch is designed to allow your engines cooling fan blades to freewheel at low temperatures when cooling is not needed, allowing the engine to warm up faster and reduce unnecessary load on the engine. As your engines temperature increases, the clutch engages to allow the fan blades to be driven by the engine and reduce engine temperatures. A failed fan clutch can lead to additional engine load when not required, reducing engine power. It can also lead to reduce cooling fan effectiveness and overheating.