I am having problems with the temperature control unit on my 2003 King Ranch. It has the automatic temperature control and the air only goes out of the defrost. It doesn't come out of the vents or the floor. I have bought a different control unit from a junk yard and it still hasn't fixed it. I brought it to a well known ford dealership they have worked on it for four total hours and haven't found how to fix it yet. They have tried a couple of things, but nothing has worked. Does anyone out there have any suggestions. Thanks the ford mechanic who has worked on fords for 30 years can't believe that he can't figure out the problem!!

 

Check out the Heating and Cooling forum. Lots of stuff there. You probably have a vacuum leak somewhere.

 

Yes, tractor_boy, you have a vacuum leak. Whether you have EATC or manual controls, the heat/cooling system is controlled by a vacuum line that runs through the firewall near the battery. No vacuum from this line to the controls and defrost is the default mode of operation.

Has the battery got a lot of corrosion on the terminals? I have seen cases here on FTE where corrosion has fallen down from the battery onto the vacuum reservoir lines and has eaten through the hoses. Take a look at this. Good luck!

 

The battery terminals are clean. When I took the module out, I turned on the engine and I could feel suction from the vacuum lines that go the the module. That means that I have enough suction from the engine.

 

That just rules out UP TO the module. What about after it?

 

KR is right, the default is to defrost. if thats what it is doing, you lost vacuum. you might have some vacuum, but maybe only half of what you need??
the black hose goes thru the firewall under the ro to the center of the glove box area. there is a TEE at that point. it is common for the hoses to dry rot or crack at that point. Also, the hose out of the module to the vacuum cylinder can be bad, but that is less common.

 

https://www.ford-trucks.com/forums/6...hlight=no+heat