This fan clutch controls the engagement of the engine fan to regulate airflow through the radiator and cooling package. It mounts on the fan drive and uses a thermostatic or viscous coupling to vary fan speed based on coolant temperature. A failing clutch causes the fan to either run continuously, reducing engine power and fuel economy, or slip, leading to overheating under load. The BorgWarner unit matches the original assembly's engagement curve, which the cooling system relies on for consistent air delivery across the operating range. On replacement, ensure the fan hub and pulley are free of runout and that the mounting bolts are torqued to specification.