Upon acceleration my 97 jeepwrangler ac stops blowing out the vents and starts blowing from defrost.

kellymac

I

0patience

Since your system is vacuum controlled, when you accelerate, it affects engine vacuum.
The vacuum reservoir has a check valve that keeps it providing vacuum to the controls for the heater.
The default position on the heating system is defrost, so if you lose vacuum, it automatically goes to defrost.

My first thought would be that the check valve on the vacuum reservoir is failing.