<VV> Early Heater

[Smitty Smith]

    From: "Devin" 
Having been a Chevy guy forever, but a Corvair owner for only the last 2
years, I am in need of some information on EM heater systems. I have
several symptoms, likely related, but I’m not sure which to tackle first.
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  Smitty says:  Devin you asked a whole book full of questions in one paragraph but I'll try to help.  First of all I have not seen an Early with all flapper door seals intact inside the heater box.  They usually got crispy a long time ago.  That means that even though the doors may be "closed" air is leaking past the edges and they are hard to shut off completely.  You are fighting a losing battle on "defrost" as long as any of your carpets are wet.  You blow hot air on wet carpets and then let that moisture laden warm air go on the cold windows and "YOU" know what happens.  The brown fuzz you mention is deteriorated insulation from inside the heater mixing box behind the firewall.  That is what contributes to the infamous "Burst-O-Fuzz on Earlies when the relatively benign flame leaps up out of the right defroster duct onto the windshield.  This occurs when operating the blower motor at intermediate speeds and the resistor coils in the right diffuser are red hot.  In
 spite of the fact that the heater will work better with that insulation in place, it will work quite well without it.  Pull the rear seat back and the two bulkhead fittings on the firewall.  Reach up inside and claw out all the insulation you can get.  Use a vacuum.  Turn the heater blower on high while you are digging it and all the 30 year old mouse carcases and droppings.  Makes a hell of a mess in the car.  The reason for cleaning this stuff out is not because of the fuzz but to keep it from "again" blocking the defroster diffusers.  Your duct hoses coming through the rocker panels (if you have a sedan)  (converts are different) attach to cast fittings at the sides of the floorboards.  Behind those grills you will find a divertor door which generally directs heat to the defrosters or the floor.  Make sure those hoses are clear for air free flow.  Those doors are cable operated from a single lever on the heater control.  As you found out, if they are not actuated fairly
 often they will lock up from moisture (rust) and you will break the lever or the cable end when you force them.
  I'm trying to make this as brief as possible but I must add, to do the job right you have to stop all air leaks, like under the rear seat and at the big hoses coming off the front of the engine. Finally the entire heater and mixing box should be removed (with the engine out).  Drill out all spot welds and taken apart.  New durable insulation installed and new rubber put on the flapper doors so they will seal.  I rivet mine together but small nuts and bolts would do.
  Finally, nothing you can do will do any good as long as you have water leaks on the carpets.  My race car has no blower motor.  In a conversation with a non believer I told him I would meet him in the dead of winter in temperatures in the teens in a T shirt and jeans just to prove I know what I am talking about.