Chasing down heater probs. Door mode acuator holds vacuum when using a pump( but very hard to push opening it by hand)and all new lines,newer water valve,thermostat. manifold vac pressure is good but when running the mode acuator does not operate and only cold air at panel vent of course. Could it be the solonoids not opening or just a bad acuator ? The solonoid closer to the firewall has continuity . The other shows 12v with the key on but no continuity with key off. I don't know what else to check . 1977 coup. Thanks

Does the actuator lever move when you apply vacuum? Are the vacuum hoses reversed? One hose opens and the other closes the door. If the lever does not move try giving it an easy push or pull. Sometimes the diaphram will stick due to age.

you might have a bad check valve. On a 76z its about 8 inches from your vacuum canister, a little valve about 1/2 in thick and about the diameter of a nickel.That was my problem along with loose clamps on the cannister itself. Good luck

The check valve is not there so hopfully thats it. Thanks. First gen , I went off a diagram from hybrid z and all seem to be hooked up correctly. The lever does move when I push it so I hope it's just a missing check valve. Now to find one.