A fan belt tensioner, also known as a drive belt or serpentine belt tensioner, is a critical component in a vehicle’s engine system. Its main function is to maintain the correct tension on the fan belt, which drives multiple engine accessories such as the alternator, power steering pump, water pump and air conditioning compressor. The tensioner ensures the belt stays tight enough to efficiently transfer power without slipping or causing damage. It typically consists of a spring-loaded arm and a pulley that adjusts automatically to keep the belt under proper tension. Over time, the tensioner can wear out or lose its spring force, leading to belt noise, poor accessory performance or even belt failure. Regular inspection and timely replacement of the fan belt tensioner are essential for reliable engine performance and to prevent costly breakdowns.