When I turn on AC (Auto mode) air blow out as normal but then went I drive at RPM up to 1500 then the air will full blast up on Defroster but not that cold and it take some time up to 3-5 min then it back to vent and it keep doing that way.
Where should I look for the problem?
What go wrong with it?

Thank you

There is a relay going out my 06 does this to

Which relay and where is the relay locat?

Check under the hood. My 2001 has a box full of fuses and relays on the drivers side firewall.

, I'm looking into the relay and on manual of Fuse panel description did not see any relay are for AC fans blower or related to the problem I'm having.....
It geting hot I need some help please.
I would thinking it may be the Vacuum leak.
I'm looking for the vacuum hose Diagram or you know where I would start.

Thank you

A/C Vacuum check valve!

Locate the vacuum hose leading from the firewall to the engine or brake booster, it shouldn't be hard to find.

+2 on the Vacuum leak

+3 on the vacuum leak

There is a vacuum line that runs between the firewall and the battery that is usually the problem otherwise it could be the controller. Here is a couple of links to some threads on this issue in another forum. Hope it helps.

http://www.f150online.com/forums/hvac/379554-air-blows-only-through-defrost.html

http://www.f150online.com/forums/hvac/381170-eatc-rebuildable.html

Man I just had that controller problem. $550 for the part.

Do you still have your old one? If so hang on to it some one may wanna trade for a rebuild. Sorry as I'm new to this forum and don't always check it every day but I will always try and help, not claiming to be the formost expert on the f-series trucks but I have some reasources as well as maintain my own and will help others anytime I can. I can suggest to any one that no matter what for specific information and make/model there are forums for the f150, gm, yota, dodge, nissan yada yada. I will help point anyone in the best direction I can or sympathize when I can't. I look at this forum as being the best in Texas fishing or fishing period and have gained as much knowlege and am thrilled to be apart of such a wonderful organization of fisher(people).

To the original post did you ever find the problem???

Check all the Vacuum line and new Vac/check valve still the same problem. Do you think it could be controler? that will be bad.

Using a vacuum pump and guage, the vacuum canister should be checked if it holds vac. As a matter of fact you should check it from the main line coming from the engine to see if it holds vac..

Still it's a vacuum leak and quite possibly be the controller but not that catastrophic. Did you check the links from my earlier post? The eatc is not that hard to rebuild. Has anyone worked on anything under the dash? Have you checked for a leak under the dash as well? Then it's possible the o-rings in the eatc could be deteriorated. I would definatly try rebuilding it before spending $550 on a new one.

Thank you for all the help from TFF member. Finally I fix it.
Thanks to 97Fordnut the web site you give are very help-full I just following the instruction and get it done . Get to Enjoy blash cold air from the vent agian
And here some of picture, just for in future some one have the same problem can do it your sefl, It very EZ





And here the instruction: I copy from the f150online.com web site(If need)
You will need, 4 new o'rings, 9/32 O.D. I found these at my local ACE Hardware store. A pair of needle nose pliers, a small straight blade screwdriver and small phillips screwdriver, a T-20 torx head driver and maybe a medium flat blade screwdriver.

With the unit out and laying on your work surface, look at the back side and you will see 2, T-20 torx head screws, remove these. Now you can lift up on the back of the unit and remove the bottom, lift the back up and pull towards you, there are 2 tabs at the front that will slide out of there respective slots.
When you get the bottom off, you will see the wire that runs from the vacuum actuators to the circuit board, unplug this from the circuit board and set the top half of the control head aside. Turn the bottom over so you can see the 10 phillips head screws, and remove all 10. Also set aside the strap that holds down the vacuum manifold.
Now lift the vacuum manifold and the actuators off the bottom of the unit, it will all lift in one piece. The black plastic unit down the middle is the vacuum manifold and there are 2 actuators on each side. Hold it so you are looking at the ends of 2 actuators away from the manifold. You will see what is a piece of foam type material with 2 metal tabs bent over, take a pair of needle nose pliers and straighten these out. Now you want to wiggle this end piece with the foam out of the actuator, I had to use a small screwdriver to GENTLY pry this end piece up and out of the actuator. It is about an inch long, and on the end that fits inside you will find the little o'ring that needs changed. DO NOT TURN THE MANIFOLD OVER, THERE IS A SPRING AND PLUNGER IN THERE DON"T LOSE THEM. Take the old o'ring off and replace with a new one. I sprayed a little silicone on my fingers and wiped around the new o'ring to help seat it back in. DO NOT USE PETROLEUM BASED GREASE OR OILS TO LUBRICATE THE O"RINGS. You want this clean and no oil on it when back in.

With the new o'ring installed, insert this back into the actuator and push down until o'ring is inserted back into the chamber, it will be a tight fit. I got them in as far as I could with my fingers, then used the handle of a small screwdriver to finish seating it. Rebend the tabs over like they were and you are finished with that one. I recommend doing all 4 actuators as I found one o'ring brittle and the obvious one leaking, it came out easier than the others.
If you do them all, it may save you some problems down the road.

If you have trouble getting the new o'rings to seat all the way, just take your time, they will work, just keep using gentle pressure and all will seat. When you are finished with all 4, mount the assembly back on the control head bottom with the 10 phillips screws and don't forget to plug the wire back on
the circuit board.
Install back in the dash and check all functions to ensure they all work before buttoning up. Sit back and enjoy that blast of cold air from the vents,and be proud, you just saved a bundle of money.

I have tried to explain this as best I can, if you have any questions, feel free to ask. It really is a simple fix, takes about an hour and a half and that includes removing and reinstalling the unit in the dash for me.
Above all, take your time and do not break anything, I have no idea where parts would be available.

Outstanding problem solved

Good post informative and with pics