I have a squeaking belt. It squeaks when the AC is on and also during driving.
A squeaking belt can be quite annoying when the engine is running. If it is squeaking all of the time this can occur for a number of reasons. I would start with a visual inspection of the belt. I would also push up and down on the belt to see if it is loose. If there is much slack in the belt then it may need to be tightened. If the belt is cracked then it needs to be replaced. If the visual inspection does not turn up anything then a mechanic would usually remove the belt and spin each pulley by hand to see which one is making noise and replace it as necessary. If this is not something that you are not comfortable with you should enlist the assistance of a certified mechanic that has the experience to do so, like one from YourMechanic.
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