A/C Problem: HVAC fan goes on and off while driving

[D M]

So I had my a/c fan on full blast switched for the face vents and I noticed that it would come on and off while driving, I just replaced the blower motor and fan speed switch less than 100 miles ago and now Ive caught something interesting. It will stop blowing from whatever vent it is switched to and start blowing on the windshield whenever the I give it gas, but the funny thing is, the more gas I give it, the more air starts to come out of the vent onto the windshield. Anyone else having this problem?

 

[David Kishpaugh]

Check the manifold vacuum hoses.
Runs from the side of the manifold to a "t" on the firewall next to the battery and theres a vacuum reservoir under the battery tray.

 

[T_Hase89]

Got a vacuum leak somewhere

Edit: What he said with better detail haha

 

[Chris]

Vacuum leak indeed