Ac head unit

[corvette744]

AC head unit-Do when i have the heat at 90 and turn the temp dial down 1 degree to 89.The temp drops to cold no slight drop in temp cold or hot.I am assuming its the head unit starting to fail cannot find any info on it.Am i looking at a new unit or blend door before i start looking into it hoping someone already fixed same problem.

 

[B-train]

What year and model?

I had a 2003 that would do that for the passenger side controls and it ended up being the blend door.