Blend Door Issue
 

So, I have a weird issue with my 1996 ZJ. I did many searches and couldn't come up with anything.

The AC works fine normally.

Only when pulling my trailer (enclosed 6'x10' box trailer) and usually only when going up hill with cruise control on 70-ish mph the air when start blowing out of defrost only instead of dash vents. When I crest the hill the dash will click (assume the blend doors) and it will go back to blowing normally.

Thoughts?

Thanks,

Chris

it is a vacuum leak somewhere. sounds like a tiny one in one of the lines