So on my new-to-me 2010
Cayman
, I get a loud whistling noise from the HVAC system. But only when driving 65+ MPH, and only when the blower fan is set to 3/4 or higher in fresh air mode.
-If I'm driving slowly, doesn't happen
-If I set the fan to less than 3/4 speed or so, doesn't happen
-If I switch to recirculate air, it goes away
-If I turn the temperature level up, it seems to get less loud
Everything works fine otherwise, it's just really annoying sometimes on the highway. It sounds like it's trying to suck air around a leaky/stuck flap in the system somewhere, but the airflow seems fine. Also the interaction with road speed has me sort of stumped.
I've read the threads on the mirror whistle and window seal whistle, but this definitely seems to be in the HVAC system. Has anyone run into this before? Alternatively, is there anywhere I can find a flow diagram for the HVAC system to try to troubleshoot? For starters, where is the recirculation intake located in the interior?
Thanks for any help.
Okay, so to answer my own question, it appears to be the recirculation flap. The flap is up under the dash in the front right and is working properly, but when it's in fresh air mode air is slightly leaking past the foam seal and is making the noise. My guess is it's doing it at speed because there's a slight low pressure area that forms at the outside intake, which reduces pressure ahead of the fan and increases flow from the interior through the seal.
Since the flap is not at all easy to get to and is otherwise working well, I think I'm going to just live with it.
Do you mean where the cabin filter is?
No. The cabin filter is at the intake at the top of the HVAC box. You access it by removing the panels in the frunk.
This is at the bottom of the HVAC box, pretty much directly below the filter and the fan (as far as I can tell).
Although driving this weekend my wife swears there's also a noise coming from the passenger window seal, so maybe I've got multiple issues going on.
Okay, fixed it. It was some weird interaction between the window seal and the HVAC system, where multiple things were making noise only at speed and only with the blower on. I freakin' swear...
The window to body seal at the rear part of the door was not fully seated into the body. The rubber seal has two t-shaped sections that are supposed to press into a metal channel in the body, and one was not in place. One would think this would be easy to fix, but getting a foot of seal seated in place took about two hours of trying various methods and swearing.
The service manual offers a very unhelpful "press the seal into place." This did not work. What eventually worked was lubing up the inside of the seal well with silicone, and then using a plastic putty knife to get it seated in the channel. Everything is quiet now.
