Hi, I have a 1993 Honda Accord LX. When I press the outside air/recirculation buttons (only these two buttons brings the problem about) a humming/buzzing noise occurs. I took the glove box off and looked underneath. The blower motor/fan is still working fine. I noticed a piece of plastic just in front of the blower motor that looks like a door that is stuck in the open position. Its a moveable door but is not moving. Whatever is making the buzzing noise is associated with that piece of plastic door. My questions are: what is that door? is there another motor associated with that piece of plastic that moves it open and shut? is it a part of the whole heater assembly (thus if needing repair would I have to haul the whole unit out?) if anyone has any experience with this part and how to fix it and or where I can find replacement parts or a part number I would greatly appreciate it! thanks guys....(also when looking under there I found a serious mouse problem!! all through the heater core was stuffed with junk so I cleaned it out the best I could without removing the unit, I was also wondering how many and where the outside air inlets into the system are so I can check those and clean them as it still smells horribly of mouse urine)

 

Then you are pretty much there.....sounds like the re-circulation motor.

You can test the motor.....it maybe the mice have built a nest that is blocking the door from moving. Might remove the rod from the motor and work it open and closed a few times by hand......if you can snake a shop vac with a 1/2 piece of heater hose taped to it in to the "box" it might help get any nesting stuff out of there.

From there, there are a few AC products that you can buy that will help with getting "smells" out.