Chevrolet Repair: 95 Blazer a/c controls, s10 blazer, vacuum line

Question
The a/c controls on my 95 S10 Blazer have started acting up.  When I have the a/c on it blows from the dash like it should, but when I acellerate or raise the RPMs while climbing a hill the a/c begins to blow out of the windshield defroster as if I had changed the conrols to defrost.  When the engine returns to normal RPMs it goes back to blowing through the dash.
I am assuming this has something to do with vacume but where should I begin my search?
Under the hood or in the dash?
I am hoping under the hood since the dash looks like it may be a trick to get off.
Thanks for your time.


Answer
Start under the hood.

What mechanical work or ANY kind of work has been performed on the vehicle recently ?. As most problems that occur after a recent repair was made can be traced back to the area of where the repair was made as a vacuum line may have been knocked loose or a wire connection came loose, Look around in the area where work was performed.

Once you locate the vacuum line that goes thru the firewall that feeds the dsh controls and if you are a smoker you can blow smoke into this vacuum line that goes into the dash and watch to see where the smoke comes out from.

this is an old mechanics trick that still works very well.


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