So I'm hoping I already know the answer to this...but I was working on my car yesterday, messing with the headlights. I had the bumper off for roughly 1.5 hours. Parked in the shade under trees which had small leaves falling.

Everything went back together fine, but now when I use my A/C at more than about 30%, I get an annoying high pitched whistling noise. Would it be feasible for say a leaf to have gotten stuck in the A/C cabin filter or something along those lines? Nothing in the engine bay is whistling, it definitely sounds like it is coming from the center-left vent.

Any ideas? The car has 2800 miles on it, and up until yesterday when I had the bumper off, has never had any issues with whistling A/C.

 

Have you checked the cabin filter? I don't think the noise would come from that though. Is it the same sound when you have it on recirc instead of air coming from outside the car?

Might be tough taking it to the dealer with your tune on the car. I'm not sure if they would hook it up to the computer or not.

 

I found it!

Nothing in the filter or anything. It was the same in any mode. Turned out to be a little imperfection in the back of one of the vent lines...like a little piece of plastic sticking out that hadn't been trimmed perfectly. Not sure why it took until now to start making noise...but I trimmed it up with an exacto knife, and good to go!