OK, this will not fix a blend door problem or a vacuum leak anywhere except in the control head of the EATC unit. So, if you have done all the tests, and are sure it is the control head that is leaking, this will save you a few hundred dollars. I am going to assume you know how to remove and install the control head, so we will start with the unit on a clean and workable surface. I did not take pictures as when I did this, it was strictly exploratory surgery. I wish I had of.
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.
devilsrighthand, aka Mike