air conditioning

[99 4X4]

My uncles 99 f150 is acting a little strange. When he steps on the gas, the air conditioning comes out of the defroster vents. Anyone have a clue whats going on? Thanks

[torkum]

Check for a vacuum leak, the most common is the hose that goes around the side of the battery comes apart.

[LxMan1]

Sounds like a broken vacuum line near the firewall behind the battery that goes to the vacuum canister in the wheelwell. It holds vacuum for low vacuum situations like acceleration.

[steve(ill)]

http://www.ford-trucks.com/forums/60...-crew-a-c.html

[99 4X4]

Thanks for your help guys, il let him know. Sorry i didnt notice there was a post just like mine before i posted.

[edgl]

It is a vacuum leak. It could be a hose or a vacuum delay valve. What happens when you step on the gas, the vacuum goes away, and the A/C goes to the defrost mode.