Q: Rattling noise inside engine when AC/Heater/Air on

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Hi there!

For the past maybe year or so I've been having this weird rattling under the hood that happens when either the AC, Heater, or if I'm 'circulating' air (not on hot or cold air). The noise appears when the car is turned on after being used (not cold) for about 5 seconds and goes away. I had a listen to where the noise appears to be coming from and it sounds as though it's coming from the top left corner behind. The sound almost sounds like a rock in a can being rattled.

Any help would be greatly appreciated! Thank you!

My car has 154000 miles.
My car has an automatic transmission.

You may have a serpentine belt or tensioner issue and may need to have them replaced but first should have a mechanic like one from YourMechanic diagnose the problem to verify the noise.

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