Steve,

The "head" is Ford's terminology for the A/C Heater control panel on the dash (the ****). The elevated cost is for the electronic automatic temperature control version in the Lariate. The unit had a vacuum leak on the inside of the controller. The black hose is the vacuum supply to the head. The unit then diverts the vacuum to the appropriate vacuum motor. The "leak" was inside the head and did not provide sufficient vacuum to the red hose. The red hose supplies vacuum to the motor above the accelerator. This motor diverts air from the defrost to the dash vents.

 

How do you test?

I also have lost the front 4X4 auto select at times. Today started it up, no dash vents. Parked it for 5 hours got back in and we had dash vents for about 30 mins of driving then back to defalt defrost vents.

So it sounds like it controls the auto hubs also??

 

Musher,

The A/C control unit does not affect the 4-wheel drive. I am not sure how to test the electronic A/C control. I had the dealer do this. Prior to taking the vehicle to the dealer, I ensured I had good vacuum supply to the control on the dash. The black vacuum hose is the supply hose. A red vacuum hose runs from the control to a vacuum motor above the accelerator. This motor controls the airflow between the defrost and dash vents. If there is no supply vacuum, check the lines under the hood.

 

I was told the "Automatic" hubs were vacuum operated w/electronic control switch. I take it this is not the case?

 

engagement of the front axle on the 4 x 4 is done with a vacuum hose to a air piston on the axle. it is vacuum controlled, but has nothing to do with the vacuum operated dash vents, exccept that they both get vacuum from the intake manifold of the engine.

 

I'm confused, I thought the vacuum came from a vacuum pump? Therefore potentially a faulty pump? Can't immagine coming from a manifold on a '00 diesel?

 

Musher the Powerstroke does use a vacuum pump and they die occasionally.
You might want to post in either the Superduty or diesel forums which are a ways further down on the main forum page. The guys in there will probably have some good ideas for you.