What is a potential cause for a slipping A/C belt?

The potential cause for a slipping A/C belt is improper tension adjustment. The tension of the A/C belt is critical for ensuring it maintains contact with the pulleys and operates efficiently. If the belt is too loose, it may not grip the pulleys adequately, leading to slippage. This slippage can result in decreased performance of the air conditioning system and potential damage to both the belt and the pulleys over time.

In contrast, while a defective compressor or leaking refrigerant can cause issues in the A/C system's operation, they do not directly impact the tension of the belt. Additionally, a faulty thermostat influences temperature control rather than belt tension. Therefore, the adjustment of the belt's tension is the primary factor that causes slipping, making it the correct answer.