Noticed a faint high pitched sound today coming from the vents with the heat on . Disappeared when I turned the air off . The kind of noise u barely notice unless you're focused on it. Didn't find much on here when I searched that description ... Any ideas what it could be causing this ?:icon _werd:

 

Trying completely closing all your windows. One might be just slightly open causing that sound.

 

The door to the air filter is not sealing correctly. I had this issue after a service at the dealer. Complained but nothing was done to resolve the issue. Eventually I dropped the glove box, opened the cabin filter door, removed the filter, cleaned it and then re-installed. faint high pitch whistle was gone.

 

Does the noise change with blower fan speed, vehicle speed, or outside wind speed?

If it changes with fan speed, I'd suspect either the blower motor has a dry bushing or, as mentioned by Viper1966 above, air is getting sucked past an opening such as the cabin air filter door.

-Rod

 

After a bit of cajoling, the dealer replaced the blower motor under warranty. Noise gone!!
https://dodgeforum.com/forum/3rd-gen...t-durango.html