While the engine is out, I've been cleaning up the engine bay. There is a flap in the fire wall that opens towards the engine bay on the passenger's side just below the heater. What is it, what does it do and is it supposed to be connected to something? I'd rather deal with it now rather than after the engine is back in.
'82 5 spd; blk/blk
That is the DRAIN to let water escape from the area at the base of the
windshield. When it gets blocked by leaves and debris the water level rises
until it runs inside the car through the blower housing and drains on the fuse
/relay board passenger floor !
The opening is intended to allow rain and wash water to escape from the HVAC
plenum. If the opening gets plugged by leaves and assorted debris, the inside of
the car gets wet. This can cause serious problems with the Central Electric
Cleaning the junk out annually should be on every owner's routine maintenance list.
The flap is intended to act as a one-way valve, to prevent hot, smelly air from the engine compartment from being pulled into the HVAC plenum.
Wally is right- this is an annual maintenance issue and often overlooked by most owners.
Do yourself a favor and remove the heater fan. It is only held in place by three bolts. Once it is removed you will be able to clean the area. I suspect even if there are not any visible leaves once the fan is out you will see a lot of dirt and debris. All this stuff is being sucked up into the heating and cooling system and both reducing the air flow and polluting the cabin. Once the fan is out you will be able to get a vacuum in behind the cooling core of the A/C and will find a bunch of debris there as well.
Removing the fan is about a 20 minute job. The space between the fan and heating unit is connected with a removable rubber boot. Once the boot is out of the way it will be obvious how to remove the fan. There connectors in the area that also get corroded and are worth cleaning up as well.
The rubber drain boot can be removed and should reveal a bunch of debris as well. This whole system is a very bad design. Newer systems now have filters preventing dirt and dust from getting into the car in the first place. While I have not engine this far, I have been thinking of designing a filter to go in front of blower for this purpose.
Dan the Pod Guy