I took out my HVAC box (under dash) so I could sound proof my firewall. After a slight cuss fest, I got it out, sound proofed the firewall and was going to put it right back in. Well, an emergency came up and I had to leave for almost a week. Now back at it, I don't remember which of the 4 vacuum lines goes where.


Orange and blue (paired)


yellow and red (paired)


I can't seem to find a schematic or diagram anywhere to match these colors to their designated spot.

 

Maybe this will help?

 

Thanks for posting those pictures, I saved them for reference.

While we are on AC systems, how hard is it to access spark plugs on a 429/460 in our trucks when using the stock AC system?

 

PITA, will have to use a swivel joint and lots of patiance and it might be easier going in from the fenderwell?

 

Bingo!


Thanks a ton! I really appreciate it!

 

The vacuum systems are a little different between the 73 mid-75 and mid-75 up factory A/C systems. Easy way to tell which system you have is the hot water valve in the heater hose has two vacuum lines in the early system and one for the later system.
The schematic that Rich posted is for the early system.
I don't have a schematic of the later system but here are a couple of pictures I took while tearing down a later system that I rebuilt. You can see the color traces on the vacuum lines.