Good Afternoon all,

2000 Ford F-150 base 4.2

My truck started to blow the air/heat out the defroster and now it stays blowing out the defrost vents and not the panel vents. After some simple googling it says the system is Vacumn Actuated and it’s possibly a hose leak but I can’t find any diagrams of those hoses for the 4.2. I thought this might have something to do with it.

Because one of the hoses running to it was so old that it was collapsing on itself.

as seen here but once I replaced it, nothing changed. The air still only blows out the defroster. Any help would be appreciated!

 

Hi. Follow this link to learn more about checking and possibly bypassing the original vacuum lines that might have broken.

https://www.f150forum.com/f6/wheres-vacuum-lne-550597/

 

Those hoses that are collapsing are for the EVAP
The one that goes into the firewall is the one you need to check and it's vacuum reservoir
Most times the one way check valve fails or the reservoir gets a crack in it and no longer holds vacuum
A hand held vacuum pump is what you need to make the testing easier
That will allow you to suck down the can and see if it holds vacuum to start the testing
Your 2000 has 2 vacuum reservoirs most likely
One attached to the battery tray and one is inside the inner fender liner on the passenger side behind the battery tray
The hoses crack and the tanks crack
Ignorant job, but pull the inner fender out to fix it, if you find that the tank does not hold vacuum
Have fun

 

I don't know if yours is the same, this is for my 1999 4.2.