What can cause a knocking noise and when you put the a/c on it goes away
My car has 128000 miles.
My car has an automatic transmission.
The most common cause for a noise to go away when the air conditioner is turned on is a faulty compressor clutch. There could also be a problem with a belt tensioner, or one of the other belt driven components. It would be advised to have it checked out by a certified mechanic, like the ones available from YourMechanic, to diagnose the noise firsthand for an accurate repair.
Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing