dash noise "FROG" 1995 chevy blazer

I have a "bull frog" noise "Barr-roop!-Barr-oop"! coming from the top of my dash near the defrost vent. It happens when I excellerate slightly and the air vent goes from in my face to defrost by itself. What the HEY! is this noise? Is it some kind of vacuum control under my dash? Could this be from the Vac.-Ball bolted under the hood? I don't think so. HELP!!! TKS> Hopey

Welcome to AF.
First thing check all vacuum lines/hoses from engine to heater controls and vacuum check valve plus that vacuum ball. They are known to leak vacuum.
MT

Thanks Mt-2500. I Did That Allready. So No One Knows What Might Be Under The Dash Making That Noise. Maybe You Mean There Is Nothing Under The Dash To Make That Noise? So! I'll Replace The Vacuum Ball. Hopeybt3

There is vacuum controls under there but make sure the are getting good vacuum from the engine first.
Good luck.
MT