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I've begun re-installing the A/C ducting on my 73 & there is a 3/4" to 1" gap between the defroster duct that attaches to the dash & the diverter duct just below it. Is this as it should be & if so does anyone have a suggestion on how to seal this gap?
Be careful sealing that with anything stiff. I'd use the foam that GM used everywhere else on the A/C system. I'm only saying that, because it seemed the whole A/C - Heater duct system was designed to have some 'play' in it, because the dash relies on this for support and visa-versa.
I thought I was smart, sealing everything with aluminum tape and then screws to firm it up, but then found out, that the center console and other externalities, suddenly didn't want to fit. Does the gap seal or get smaller, when you push the diverter duct back towards the firewall? Did you seat the bottom section down too firmly? I had a 1/4 inch to 1/2 gap when I was done, but it sure took a lot of playing around with everything again and again....
I used aluminum duct tape to close the gap. Made no sense to me to have all that air escaping behind the dash and going nowhere so I closed it up
Seems to work better for sure.... But getting it apart is a bit more difficult. We see them in the shop both ways and when they come in that way we use the black duct tape.. so they leave he way they came.