After replacing the vacuum heater control valve and hoses on my '78, the heater doors will not close when I switch to vent or A/C. They worked fine before doing this.

The heater works well as does the A/C. No leaks from either the valve or hoses.

Before replacing the A/C bezel, I lubricated the fan speed, temperature and selector mechanisms with lithium grease. The only thing I have noticed was that after replacing the A/C bezel, the selector switch doesn't seem to fit into some of the notches as securely as before.

Any ideas as to what could be the problem?

Do you mean the little doors that are on the heater outlets on either side of the console, by your feet? Mine are fixed. If you mean the selector flap inside, then it may not be moving enough because of an old dashpot. The flap itsef may have worn edges and not seal enough to guide the air properly.

My selector doesn't click into the notches at all. I think there's a spring-loaded thingy that gos into the notches? Mine is totally missing and I would have to fabricate something, but have no photo or diagram to go on.

Can you please explain what you've got or get some photos, because I can't find any photos of what is supposed to be there.

thxZ

I was thinking the problem was the two doors for the heater outlets not closing when using the A/C or vent. I saw that there is a cable/linkage between the selector lever and the driver's side heater outlet door mechanism that opens and closes the doors when moving to/from defrost mode.

I've since been reliably informed after an inspection of my system that these doors are in fact supposed to stay open unless the defroster is selected.

Apparently the inner door or selector flap inside the heater box is not closing and/or sealing properly, thus the reduced air volume through the dash vents.

Thanks!