I have tried every possible combination and still can not get any air from my center vents,directly over the climate controls.No a/c or fresh air at all.Its a 1980 300SD,Help,Please!

Mine does the same thing if I don't shut everything off before I turn the key off (30 seconds or so before) and then let it run 30 seconds or so before I turn the ac on. Might give that a try but the problem is one of the vacuum pods that moves the flaps in the vents is going bad. You can wedge the flap open if you can get to it..... should be able to reach it (although not very well) from the passengers side if you remove the kick panel. Good luck.

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1985 300D Turbo ~225k
2000 F350 (Powerstroke) 4X4, SWB, CC, SRW, 6spd ~148k
1999 International 4900, DT466e (250hp/660 ft/lbs), Allison MD3060 ~73k