Some customers may complain about a clunk coming from under the hood when they are not moving or at low speeds. The noise is related to the A/C compressor engaging the clutch so the refrigerant can be moved around the system. Some noise is normal. But, if the drive belt or tensioner are worn it can make the noise louder. Andrew Markel covers how to diagnose the drive belt system and compressor. Sponsored by INA, a Schaeffler brand.