76 280z with vacuum operated heat/ac controls. however, i have absolutly no vacuum comin or going throught the hoses. my a/c works, but air will blow through the center vents only. other than that i got nothin. ive hooked and unhooked everything i can think of and checked this site over... does anyone know what i need to replace to restore the vacuum to my lines?

maybe this will help-

it discusses the origin of Vacuum, a good place to start.

http://www.classiczcars.com/forums/showthread.php?t=18365&highlight=ac+vacuum+lines

Are you saying that you can't get air to flow through the window defrosters?

I also have this problem on my '76 and would be very interested in a solution!

yup... i get no flow through the defrosters or the side eyeball vents, and no vaccuum from any of the hoses that go to the control unit. but it blows like mad through the center vents. and it only blows cold air from the a/c, or normal temp air...but no heat. i have vacuum going from the intake to the canister, but no where else. so i checked out these diagrams:

http://www.zcar.com/forums/read.php?f=1&i=545965&t=545965

i pulled the hose from the canister through the firewall and have vacuum through it. the problem is one diagram says that hose goes to a magnet valve, and the other one says it goes straight to the control unit. so instead of contorting my body in strange ways to get under the dash, im gonna try the straight to the control unit first thing in the mornin. btw..i looked for this magnet valve thingy and i dont have a clue what it is or see anything that even resembles it.... anybody know?

oh, and one more thing...there is apparently a soleliod that the hoses are supposed to pass through...i dont think i have that on the car...least not now... anybody know what it does or where its located?

Yep yep same deal, though I can get heat, and it seems like I also get flow through the eyeballs sometimes too... 'could be my imagination though.

I can also, sometimes, IF, I'm lucky get it to switch over to the defrost... this has not happened in months though, and I'm beginning to think my getting it to switch over was merely luck.

The vacuum slenoids are under the hood on the right side by the fuse links. The vacuum can should be underneath.

I am not sure if your issue was like mind but look at this link. http://www.classiczcars.com/forums/showthread.php?t=22679

it was the vacuum line through the firewall...that mixed in with a couple of broke down hoses...and all works good.