in my wifes 99 blazer when you are accelerating the blower motor slows way down until you ease up on the throttle.could this be a vaccum leak?i didnt think the motor was controlled by vaccum.

 

Time for a dumb question: is the motor actually slowing down, or are you just feeling less air through the vents? It's easy to be fooled by changing acoustics as the vent control system re-routes the air flow to different outlets for A/C, defrost, etc.
Although the motor speed is not controlled by vacuum, the duct system is. Recently, my Blazer would blow cold air on my feet for several minutes after turning the A/C on. Turned out to be the vacuum hose between the intake manifold and the vacuum reservior, a bulb-like affair attached to the hood. Two of the hoses had turned into a sticky dust; replacing them solved the problem. If your hoses are leaking, the drop in vacuum during acceleration may aggravate the lack of vacuum and cause the vent system to temporarily change the air flow, which would then return to normal once manifold vacuum increases as you reach crusing speed.

 

did not even think of that.i just know on a/c it slowed out of the vents.i replaced some of the vac. lines because 4 wheel was acting up but did not change the hard ones yet will have to do that when it cools down out. its hotter than h### in pa.i will have fix soon though wife is pregnant and she uses this to deliver mail.thanks for the help

 

Our pleasure.

 

ok i changed the vaccum lines at the brake booster to down under the front bumper.but now it wont change at all when you turn the control you hear nothing in the dash changing.any ideas?all other vac lines look fine.

 

Is the vacuum line connected to the vacuum reservoir that is mounted *inside* the driver side fender?

 

yeah that is connected.i found that problem when my 4wd. would not engage.i looked at the acttuator under the dash.i have vaccum and it is moving its just not shutting the air off completely.but it semms to move all the way.at least it dont change under load any more.thanks for the help.this forum is really helpful for trouble shoooting and advise.thanks again