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Rattling sound when I turn off my heat or AC fan

When my fan speed is at 0 or off there’s a rattle on my car immediately when I turn it on it’ll stop. Could this be a loose heat shield or something

That sounds more like a faulty hvac door actuator to me. GM product?

Yes Toyota / GM made car. Would a video help with sound pinpoint better

Sure it will! Is this a Chevy Prizm you are talking about? Same as Corolla but a little cheapely made.

Suggest to post make/model/year/engine/transmission

Chevy
prizm
2002
1.8 [L] Toyota 1ZZ-FE

If this only starts when the fan is turned on then I would suspect something that is actually in the fan motor cage that may be bouncing around. I had that happen with a mouse that was in there once. Not hard to pull and take a look. Something like a heat shield would make noise even with the fan off.

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The hvac fan-speed isn’t related to the exhaust head shield. Heat shields are a common rattle source though. One idea, when you turn the fan on it makes enough noise you can no longer hear the heat-shield rattle. Ask your shop to put your car on a lift & verify the heat shield is solidly attached.

No once I turn my fans OFF a metal rattling under the passenger front tire starts. Once I turn the heater/air ON it will NOT rattle at all. It’ll stop if fans are going.

Does it do that while stopped and idling and/or while driving? Is it possible that the blower motor drowns out the sound of the rattling when running?

Once the fan is OFF it’ll rattle in drive/Idle etc
Once fan is on it’ll stop even in idle

I mean yeah blower motor could be it because it’s clear this is a fan related problem of some sort