WeasleVette454

While I had my seats out (replacing the cushions and covers) I decided to visit this heat problem. I decided to pursue the route posted by vettefixr but I had one nagging question.....my heat problem isn't from seepage or radiant transfer, it's coming directly out of the HVAC duct opening that is behind the radio. There is no air flow at idle (switch off, of course) it's only when driving (switch off, of course).

So, aside from installing water shut off valves, what are some recommendations? Why is any air whatsoever coming out of my HVAC duct when the motor is off? Thanks!!!

Weasle

Mike Mercury

just solved this exact problem with the wifes 1973 (with AC). The heater-core copper connection tubes exit out the bottom of the airbox. This "exit channel" for the heater-core tubes needs to be sealed, or air will flow through it when driving - and come out the AC ducts. It's air from the engine bay, so it's heated. I could hold my hand over the air duct and feel moderate air flow when driving; but wasn't there when not moving.

I bought a can of that expanding foam in-a-can and sealed off the the channel from underneath . It totally solved the problem. There are many types of the foam sealant; and I used the LEAST expanding variety of it. The can said it's safe to 250 degrees; and our useage of the car... that is plenty safe. I rubber-gloved my hand (no jokes... please ) and sprayed soem of the foam around - then smoothed it out with my protected hand; pushing it into all the corners and up against the heater-core connection tubes. It didn't take all that much of the foam sealant; mainly because the heater-core tubes fill much of the open passage already.

If you just want to run a test, take some foam rubber and stuff the channel around the heater-core water tubes underneath the airbox and go on a quick ride to see if the unwanted airflow in the ducts is gone.


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[Modified by Mike Mercury, 6:40 PM 7/4/2004]

vettfixr

The air you are feeling is the result of the high pressure area at the heater intake. The movement of the car causes the air to flow through the system even when you have the fan off. All the seals to the heater box and heater core and internal to the heater/AC box should be in good working order but I'll bet that if you pursue my fix you will see a big difference. It's a cheap fix (under $10) and I would recommend it to all C3 drivers if they're having a heat problem.