AC vents in cab won’t open

[boomerzoomer]

Recently the dash vent ducts stopped opening in my 2000 Minnie Winnie DL. At first while the AC was working normally the ducts would close during passing gear acceleration. Then the AC would open to normal once it dropped out of passing gear. Now the ducts won’t open at all. The AC is literally blowing cold air inside the dash with nothing from the dash vents. Changing the air flow knob from floor, dash, or mix does nothing. Anyone else have this problem?

[Hgrace56]

Sounds like a vacuum problem

[guardrail53]

Originally Posted by Hgrace56

Sounds like a vacuum problem

X-2, ^^^^^^^!! Check under your hood for a broken vacuum line, if none show them self's, you will have to pull your heater control out of the dash and check that you have vacuum to it! A vacuum leak will cause more problems than your dash controls not working! It will also make your motor not run right also!

A old school way to find a broken vacuum line is start your engine, take a can of ether/starting fluid and spray it around the intake manifold, listening for a change of RPM, running faster, and look really close when you find a spot that the RPM's come up! Look for a broke vacuum line, most of the time, they get hard, split, at the end, and come off, and you can cut them back, and put them back on, as a temp fix, till you go to the Auto Parts store to buy a roll of new vacuum line! Hope this helps you! Rail!

[boomerzoomer]

Sounds simple enough. A vacuum line issue. Thanks SO MUCH !

[A32Deuce]

Another way to find, because of so many lines, find a shop that has a smoke machine for that reason. Easier and faster finding a bad hose. Searching around by hand, you could pull off a hose and compound your problem. Just a thought.