On my 2004 F250 with 70,000 miles when i switch my truck in to 4wd with the a/c on it switches from blowing out the dash vents to the defroster vents. when i switch back to 2wd the air starts to blow back out the dash vents. Do you guys have any idea why this is or how to fix it? Thanks

 

You have a vacuum leak. It is probably in one of your hubs. Default with no vacuum goes to the defrost mode.

 

If you're lucky it's a hub, otherwise you're chasing a vacuum leak all over the engine bay. There's a T joint that is common too. Basically you're not in 4wd if your defrost vents come on when you use the auto-selector. Mine is about 50/50, so normally I'll get out and switch the hubs manually. Remember, you need to move about 6" for the hubs to engage, so plan ahead.

 

When ever I turn the defroster on it blows a/c. If I switch to a vent position it is just outside air. Is this normal?

 

Yes, a/c comes on with defroster to remove moisture.

 

Thanks, one less thing to think about.

 

Thanks alot 69cj,when my auto hubs went bad for the second time i replaced them with manual ones therefore i dont have any vacuum how can i fix this or should i just let it alone.

 

1st you need to isolate the leak. Does the vacuum pump run cont? If so, disconnect vacuum line at the pump and put your finger over the pump outlet. If the pump stops the leak is in a line or device. If the pump continues to run or never did run then you have a bad pump. Before changing pump, make sure it is getting voltage. If not, check fuse. If the pump is good then keep expanding your search til the pump shuts down. Make sure that your hub vacuum lines are not leaking, check the vacuum line at the heater control valve and a vacuum connection behind the glove box door. These are common leak points. Hope this helps. Good luck.

 

Did you ever get this problem repaired? If so will you please tell me what you found to be the problem. My 2004 King Ranch is doing the exact same thing. It also periodically blows #45 fuse.
Thanks you for any help...

 

Inner right side fender white plastic deal with wires and vac lines from the vacum canister is bad

 

Mine too, just noticed it yesterday.

Subscribed.

 

you can use a MityVac hand pump to pull a vac see if it holds vac

The last Guy that had this Issue was the Vac Control Silinoid

he could switch to 4X4 the hubs would lock IN but vents would go to defrost

If you switch into 4X4 and hubs dont lock you likely have a Leak in the Hub seal or Vac line to Hub

 

I had the same issue. Chech this tread out.
https://www.ford-trucks.com/forums/1104986-esof.html
Thanks to Mike Chan I got it fixed right the first time.

 

John, did you ever get around to replacing your PVH solenoid?

 

Yes I did. Picked up a new one off eBay. Still in the box for $59' plus shipping.