1970 Charger HVAC questions....

[Kern Dog]

Hello everyone,
I finally got the fan to spin for my heater/A-C system after replacing the vacuum switch. Strange thing is, the fan only blows in the A/C and Max A/C settings. The fan stops when I press either the Heat or Defroster buttons. The heater box has never been out of the car but the dash side vacuum lines look fine. I replaced the vacuum lines on the engine side but with no clear listing anywhere of the correct route, I just did what I thought made sense.
From a manifold vacuum port on the carburetor, I ran a line to the small vacuum can. Halfway to the can, the line has a T that allows a separate line pass through the firewall. On the vacuum can, the other nipple has a line that also runs through the firewall with a T that has a line going to a thermo valve on the firewall.
I am totally new to these vacuum/electric type heater systems. I'm confused as to why the fan only works on the A/C function.
Any helpful guidance out there? YouTube was no help!

 

[hawkeye]

You don't have a vacuum problem, it's electrical. Did you use a new switch?

 

[Kern Dog]

Yes I did. The old one had really stiff buttons. The "new" one was at least 14 years old though, still in the box from when I bought it in 2001.