EATC o-ring repair - How to... with pics.

[ncmm]

This is an excellent thread. Thanks to all who've contributed.

I had the air out of the defrost under acceleration symptom. Ran the EATC self test. No codes, just 888 with everything else lit. Decided to replace o-rings last weekend. Easy to do with all these pics! Used silicone orings and a bit of dielectric grease on them as recommended. All back together and worked fine for about 15 minutes. Then fan went full blast like it was in max mode. Tried lowering speed but it took several up and downs of fan dial to lower speed. A few minutes later same thing. . .rats. Air blows out of correct vents selected, sometimes a few surges before going full blast. I do remember the foam under the tabs was a bit beat up on one. EATC self test still good. Any ideas where to go from here? Thanks!

[fastblackmerc]

This is an excellent thread. Thanks to all who've contributed.

I had the air out of the defrost under acceleration symptom. Ran the EATC self test. No codes, just 888 with everything else lit. Decided to replace o-rings last weekend. Easy to do with all these pics! Used silicone orings and a bit of dielectric grease on them as recommended. All back together and worked fine for about 15 minutes. Then fan went full blast like it was in max mode. Tried lowering speed but it took several up and downs of fan dial to lower speed. A few minutes later same thing. . .rats. Air blows out of correct vents selected, sometimes a few surges before going full blast. I do remember the foam under the tabs was a bit beat up on one. EATC self test still good. Any ideas where to go from here? Thanks!

The foam has nothing to do with the blower speeds.

One of two things could be wrong.

1 - Blower Control Module could be going bad.

2 - The electronics inside the EATC can be going bad.

[linclsc]

Thanks. Glad I looked it up on the site. Saved a lot of money and took no time. Fixed mine before vacation.

[Nutfield]

I replaced the o-rings (silicone o-rings from Grainger), no change, still blowing only through defrost vent under all conditions. Next I blew out the vacuum tubes with compressed air and sealed the vacuum connector to the EATC with dielectric grease. Still no luck. The original o-rings were all still pliable and the filter foam on the solenoids was still good.
Finally bit the bullet and bought a Dorman remanufactured EATC. Now all is good. And I still saved about $600 over going to a dealer due to all of the good info here.
Thanks.

[Rockettman]

What size (or "#") o-ring is required?

[NavySeabee]

What size (or "#") o-ring is required?

http://www.grainger.com/Grainger/ORing-1REC2

[racorcey]

I replaced the o-rings (silicone o-rings from Grainger), no change, still blowing only through defrost vent under all conditions. Next I blew out the vacuum tubes with compressed air and sealed the vacuum connector to the EATC with dielectric grease. Still no luck. The original o-rings were all still pliable and the filter foam on the solenoids was still good.
Finally bit the bullet and bought a Dorman remanufactured EATC. Now all is good. And I still saved about $600 over going to a dealer due to all of the good info here.
Thanks.

You may have been victim to the same problem I had. It is the lesser found of this particular problem. O-rings and other fixes won't help. What I found, after going through all the otherwise great fixes, was that the plastic valve body, on which the solenoids and O-rings sit, was defective. That is, there were hairline cracks along the molding lines. I tried using RTV, but it doesn't adhere well to most plastics, and if the crack is under the solenoid, you are SOL. I found a used control head and basically used the plastic body with my otherwise rebuilt original control head to fix the problem.

I documented this particular problem about 2 summers ago. By then, I found at least several more MM posters with this exact problem.

[Nutfield]

You may have been victim to the same problem I had. It is the lesser found of this particular problem. O-rings and other fixes won't help. What I found, after going through all the otherwise great fixes, was that the plastic valve body, on which the solenoids and O-rings sit, was defective. That is, there were hairline cracks along the molding lines. I tried using RTV, but it doesn't adhere well to most plastics, and if the crack is under the solenoid, you are SOL. I found a used control head and basically used the plastic body with my otherwise rebuilt original control head to fix the problem.

I documented this particular problem about 2 summers ago. By then, I found at least several more MM posters with this exact problem.

Thanks for the info. I will keep this in mind if the problem recurs with the remanufactured EATC. Still, $239 after my core refund isn't too bad. I have been a Ford fan since before I bought a new 5.0 Mustang LX in 1990 (still have it) and this EATC may be the worst design that I have ever seen, and I was dumb enough to buy a '04 Freestar, so that's saying a lot.
Btw, my car is a '08 Crown Vic. MercuryMaurader.net had the best info for this problem.

[VMARAUDER]

Anyone know which solenoid controls each function? I replaced the o rings and air does not come through the vent but all others work...floor, defrost and floor/defrost

[racorcey]

No, but....you could try hooking up a hose to each one and try sucking/blowing through each valve. With no voltage applied to each solenoid, I believe that the valves are in the closed position (although I can be wrong on this). Even so, if it is the reverse, you could apply 12 volts to each individual solenoid and then try the suck/blow test again.

Bottom line - if any of them leak, either the o-ring was not installed correctly, or you might just have a crack in the plastic manifold - just like the problem I had.

You could also check the continuity of each solenoid with an ohm-meter to insure they're all the same.

Otherwise, you may be looking at bad (electronic) controller.

Heck - at least the weather has cooled down somewhat!

[VMARAUDER]

Thanks Randy...continuity check was ok so I will just redo it later

[Billboard]

Another happy owner here, I had defrost only, replaced O-rings now everything is back to normal. The job took less time than I thought.

[Black_Noise]

yey, I made it to sticky thread level. (sorry havnt been on in a while)

[murphypeople]

After 2 years of putting up with air only coming out of the defrost vent I finally attempted this repair job. Worked like a champ!!! parts and supplies were less than $10.00 and took me 2.5 hours to do. My indy mechanic would not do the repair. And the dealership wanted $1,300. $900 just for the part. During my repair I noticed that two of the o-rings were okay and the other two were brittle. Four new silicon o-rings installed with a nice coating of dielectric grease and working great.
Now this post is excellent but for those of you that would appreciate video instruction these two links are a must.
1.) All the details including parts ordering information: https://www.youtube.com/watch?v=y0IWspXkQtE
2.) The minor dashboard work to remove the EATC: https://www.youtube.com/watch?v=S2Q0SvvE-gg.
Happy New Year!!!

[gatlandc]

This is an excellent repair blog, well done. I followed the instructions and now have cold air blowing on my face again.

One question I haven't seen asked or answered is do you think this o-ring problem could lead to a lean running condition. I also have diagnostic code 171 and 174 up!