NBS '99 a/c issues

i can't seem to get a blend of cold/warm air with my a/c. if the blend control is set to max cold the a/c cools fine. if i move the dial one "click" to warm the temperature of the air is what i would expect to
experience if i would have moved the dial about half-way.
would this most likely be caused by a failing control panel or is there something else i should consider? i just don't want to replace the controls if the problem is more likely somewhere else.
the extent of my work so far consists of charging with freon and replacing the clutch cycling switch.
any thoughts?
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Two things quickly came to mind as I read your discription of the problem. The first thing was the old foam seal is falling apart and some of it might be preventing the blend door from closing completely. The second thought was a cracked vacuum hose not allowing the actuator to pull the blend door closed. Try putting your ear next to the control head and shutting off the engine. Listen for any hissing sound indicating a leak. If you don't hear anything it means digging into the ductwork and watching the blend door and actuator while someone works the controls. I had a similar problem with my 97 Yukon SLE and it turned out to be a small crack in a vacuum hose. As I was leaving on a road trip south the next day, I just squeesed the hose to open the crack slightly and rubbed some silicone sealer into the crack as a "temporary" fix until I got back home. That was 3 years ago and it's still working fine. Good Luck, JR

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