Heater Box Buzzes

[MIPS]

Whenever the car is at cruising speed and the cold air vents are closed, the heater box makes a buzzing sound like a reed buzzing. All it takes to make it go away is to open the cold air vents a little, or slide the vent control to OFF.  Part of me thinks it's one of the box seals coming apart but I can't think of much else that could cause the racket but it's amazingly annoying.

[maddog]

I had a similar issue with my wagon and it turned out to be some leaves stuck inside the vent doors.

[TheBirdman]

For the first few months my heater vents had a distinct aroma of hantavirus, so I really should eventually take the heater box apart to clean out what is almost certainly a mouse nest. Confounded rodentia.

[MIPS]

Well now I've REALLY done it.
The heater box is sealed with sticky backed foam tape but in nearly 40 years it has perished and left behind the plastic ribbon the adhesive backing is on. THAT is the culprit for the buzzing. The seal on the passenger side vent flap in particular was making the noise and trying to pull the plastic out has caused it to sound EVEN WORSE.
Looks like I'm just gonna have to pull the whole box out and regasket it.

[MIPS]

Pulled the heater box today and found insulation plugging the core, a leaking heater core and yes, there is perished foam everywhere. WOW I fell down that rabbit hole fast.
I can source the edge stripping no problem but does anyone have a source for the larger square pieces either in sheets or precut as a kit?

[MIPS]

Nevermind, it turned out to be easier to just buy sheets of 1/8" and 1/4" foam from a shop and a can of 3M "super 77" spray adhesive. There's about 12 pieces total to replace and it takes about two hours to cut out and glue the new pieces in.

[vangremlin]

Nice work!  Enjoy the quiet and the warm air, with that new heater core the cabin of your Eagle will warm up in a hurry!!

[amarshall]

Impressive. Oh yes, the work is nice - but really I meant how quickly you are climbing back out of all these rabbit holes!