AC blowing only through the defroster (windsheild) vents

[Flight F150]

I have a 2004 Expedition 4.6, recently the AC will only blow through the defroster vents. My research leads me to believe it is a vacuum issue.

How do I check the system to see if the vaccum pump is working (where is the pump located)?

Any suggestions, help will be much appreciated.


Thanks

[Yankee7985]

There is no pump to check. Check the vacuum line that runs along the passenger side of the engine compartment on the fender well. It also goes through the firewall. It should be a small, black plastic line. Check it for cracks.

[Shinesintx]

I had the same issue on my 00 F150. Never got it fixed due to it only happened from time to time. The a/c would go through the correct vents if I turned it off and on a couple of times. The issue was a butterfly valve servo thingy that directed airflow. Sorry for the lack of technical terminology.

[po1911]

you cnn buy a cheap hand vac pump that may help you track down a pin hole leak in a specific line

[Flight F150]

Thanks for your help, I found that the vacuum tube that goes through the firewall is broken, it's very brittle . I'm thinking of replacing the entire tube that runs through the firewall. I'm not sure how difficult it will be yet.

I will keep you guys informed....

[zmurphy]

congrats on finding the issue. please keep us posted, i am having the same issue w/ my 98 Expy. i gotta make time to work on it in the week or two.

thanks

[Flight F150]

Well, I had to replace the tube running from the valve to the firewall. I also had to replace two valves, one with three connections and one with two connections. After these changes I can now control the air vents again.

Thanks

[zmurphy]

and of course you took pictures right!

thanks for the reply, did you get the replacements straight from Ford? where were the valves located?

thanks again!