99 Deville A/C

The A/C cools fine but the (underdash) controls change the air to the
defrost position instead of out the dash vents. It makes "groaning"
noises like it is trying to switch back to the dash vents but it
rarely does. I've looked for a vacuum leak under the hood and had an
A/C shop check too. Found no leaks. I wasn't able to check up under
the dash though.

Any ideas?

On Jan 24, 7:29 pm, Jack <j... RemoveThis @bellsouth.net> wrote:
> The A/C cools fine but the (underdash) controls change the air to the
> defrost position instead of out the dash vents.  It makes "groaning"
> noises like it is trying to switch back to the dash vents but it
> rarely does.  I've looked for a vacuum leak under the hood and had an
> A/C shop check too.  Found no leaks.  I wasn't able to check up under
> the dash though.
>
> Any ideas?

Is the mode being manually selected, If it happens in 'auto' it will
blow where it feels it needs to. It will typically come out the dash
vents on auto when the temperature selected is at, or lower(cooling)
than the in-car temperature. Did the a/c shop check for any codes in
the a/c programmer(ACM). As far as the groaning noises, I am not sure.