What is the function of a belt tensioner?

• A. To regulate oil pressure
• B. To maintain the proper tension on the drive belt
• C. To cool the engine
• D. To lubricate moving parts

Answer: (B)

The belt tensioner is responsible for keeping the drive belt at the correct tension so the belt consistently drives accessories like the alternator, water pump, power steering pump, and A/C compressor. It uses a spring-loaded or hydraulic mechanism to apply and maintain tension, automatically adjusting as the belt wears and as engine movement occurs. This prevents the belt from slipping (which would reduce charging, cooling, or steering assist) and also avoids putting excessive load on bearings when the belt is too tight. The other options aren’t the function of a belt tensioner: oil pressure is regulated by the oil pump and relief valves, engine cooling is handled by the cooling system and water pump, and lubrication is provided by the engine oil.