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AC Fan Noise

Car seems to be making a noise that sounds like it might be coming from right behind the dash, sounds maybe like a belt. It’s a rhythmic noise that isn’t really random and it occurs pretty much at all times until I turn the fan on, then it goes away.

Any ideas as to what might need to be fixed? Thank you!

could you elaborate? Does it depend on fan speed? if you leave the fan on, does it return?

No, the sound is only made when the fan is off. Once the fan is on it goes away and when I turn it off it comes back.

Turning the fan on results in more mechanical load on the alternator, so that’s something to guess about anyway. Ask your shop to check the belt that drives the alternator for wear and proper tension. You could do some experiments turring on high electrical power circuits, like the headlights on bright, see if that makes a difference in the sound. There’s probably a relationship w/the AC compressor and the fan too, take a look at that belt’s condition as well.

It could be that the fan bearing is going south. Some fans run at a very slow speed…even if you have the switch off…to help circulate the cabin air.
At the lower speed it may make noise, but when you turn the fan speed higher the noise goes away.

You could pull the fan fuse and eliminate the fan, to see if the sound is still there.


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Also, the noise from the fan may be masking the mystery noise, ie, it may be present whenever the engine is running.

Have you tried listening under the hood? You might actually be able to tell from whence the sound is coming.

Now that’s come classy writing right there! You don’t see “from whence” used every day. Bravo!

Only on the Car Talk forum do you get that!

LOL, thanks. :smile:

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