Heating system question- 66 Mustang

[sparx]

I completed the rebuilding of my heater box today, it turned out well as best I can tell anyway. Got a new heater core that fit very well from Virginia Classic, if you ever need one. Just to be safe I added the rubber end caps on the top and the bottom of the heater core. It was a very snug fit, if it ever rattles I will just blow the car up.

While I was completing this project I was trying to understand how the air passed thru the heater box and how it functioned. I just figured out the plenum extension to the left of the heater box, (mine is all twisted and smashe, was not even connected to the heater box nor are the defrost tubes, more parts to order) delivers hot air to the floor area and up to the windshield for defrost.

The question I have then is the big round opening on the top at the right intake air?

So you would open the front door on the face of the heater box for heat or cool air or both?

I check the factory repair manual and not much info there and the owner’s manual does not show much detail as well.

Sparx

 

[2+2GT]

Yes, the big pipe that goes to the cowl is the air intake.

Below that is the fresh air/heater select door, operated by the left knob on the control. Full up or full down, not in between. The steel door facing the passenger is the fresh air door.

Get the high temp plastic defroster plenum. if the hoses and nozzles on the defrost are bad, replace them too.

With all that done, your heater will be, as a French auto writer described it in 1965, "formidable".

 

[sparx]

Thanks