Ford Repair: Air Conditioning Problem, vacuum tank, reservoir tank

Question
I have a 1997 F-150 5.4 V8
The A/C blows cold air, but as soon as you step on the gas, you can hear a vent close, and all that comes out is hot air.

The AC unit is putting out cold air, and the hoses are cold to the touch, and cold air does get into the truck.  Then within a few seconds the vent closes and only hot air comes in.

All the vents seem to work fine, and blow air where its supposed to go.  All fuses are working.

Not sure why this is?

Answer
Hello and thanks for the question...I'll try to help.
I think what's happening is that you are loosing the vacuum supply to the blend door servo when you step on the pedal. The vacuum supply tank is located on the battery tray. Check the lines going to and from it.

REMOVAL
Remove the battery and battery tray bracket.
Disconnect the A/C vacuum tank hose for the A/C vacuum reservoir tank and bracket.
Remove the screw and the A/C vacuum reservoir tank and bracket.
INSTALLATION
To install, reverse the removal procedure. NOTE: When positioning the A/C vacuum reservoir tank, make sure that the bottom locator and two top tabs align with the battery tray.

Hope this helps,
Erik