i bought a used 99 f250 v10, i went to turn on the a/c today, and it only blows where the defrost is toward the window. it gets cold after awhile, but nothing out the vents, the heat either.
any ideas?

 

4x4? Shift on the fly?

If so then you have a vacumn leak for the ESOF. Probably near the hubs.

 

Even if you don't have ESOF, you have a vacuum leak or a broken line.

The air direction doors are controlled by vacuum motors. Lack of vacuum causes them to return to their default positions, which is recirculated air through the defrost vents.

 

You either have a vacuum leak or the switch in the control panel in the dash has gone bad--more than likely a vacuum leak. Start the engine and listen for a hissing sound--both in the engine compartment and under the dash.


RON

 

yes its 4x4, what is ESOF?
its loud under the hood, i cant hear any hissing.
where would i begin to look for a leak?

 

This is correct. I had the same issue on my 2005 F350 6.0 which I traded in. It does default to blow from the defrost. Not a major repair even if you get it done at the dealer

 

ESOF is "Electronic Shift On the Fly". You have this if you shift into 4x4 by turning a little plastic **** on the dash.

If you shift into 4x4 with a manual style on the floor gear shifter, then you do not have ESOF.

This is important because the ESOF is also vacuum operated and is a common source for vacuum leaks, although usually only when it is being engaged.

I would begin looking at the vacuum tubing. Check for any melted sections, cracked rubber connectors etc...

 

Had the same issue, the jiffy lube mechanic popped a vacuum hose off right next to the oil fill cap under the hood. Put it back on and solved the problem. (after I spent $35 to replace the ac control switch on the dash.)

 

I had the same issue on my 2001 Ford F250 there is an electrical unit on the passenger side that the vacuum lines run to from the big canister then drops down to the hubs I cant remember the name of this unit but it needs to be replaced. The dealer has it for bout 100 bucks after I replaced mine the AC worked great. If you have access to a smoke machine you can check this by removing the vacuum from the big canister going to this valve or unit and if smoke comes out from the unit then its bad. Sorry I cant remember the name on this unit where the vacuum lines attach and separate for the 4X4 hubs.

 

Search keywords "PVH Solenoid".

PS. This thread was dormant for FIVE YEARS, it really didn't need to be resurrected.