Heat - Defrost Mode Control Not Working Right

[damork]

The mode control between defrost and vent started acting up and sometimes hangs when switching from one to the other. In the mornings when going from vent or floor to defrost, it usually takes a few seconds as the door or flaps make a ka-thunk sound before I get full fan blowing on the windshield. Once this is done, it switches between vent and defrost just fine until the truck is shut off.

I've replaced the mode motor just above and to the right of the accelerator pedal, but that was not it.

The dealer parts books show levers connected to mode door shafts - do these fail or is more major work required to correct this?

Thanks.

[MikeChase]

The mode door lever on our 96 Suburban somehow became disconnected - it still kinda worked but slowly and without full travel. Resulted in very limited blower output in one position. Yours may have the same problem. Difficult to see down there but it's an easy fix - just reconnect. Try watching the linkage while shifting between modes.