I'm not sure how, because I'm not a Tech, but I would check the main line Vacuum from Engine head to the Vacuum champer to see any crack hose or leaked *the vacuum champer is behind the Battery* from The Vacuum champer to firerwall there is like vacuum check valve (i think) (I went to Auto junk yard get one from any old FORD with the same size hose will work to test)
*when you are disconnetct the hose form firerwall to Vacuum champer you will here the air sound that mean it is holding vacuum*
Good luck

 

Thanks to all who have contributed to this thread. I experienced the switching to defrost and back and had gone to the Internet to see if I could find anything out about this. So after a brief bit of trying to find the correct combination of key words, this thread pops up. Having some time, I went to Ace Hardware and dropped $2.00 on some O-rings. Got home and after about an hour of work, I had completed the O-ring replacement and put all back together again. Who knows how much I would have been charged at the dealer for a replacement ETAC module.
Now to find if there are any other leaks in the hoses somewhere. That will be found by driving and using the A/C.

 

I am just so thankful for this help. I have been without lower air vents for over a year and the Panel vents went out this week. I bought the 100 piece pack from Grainger and it worked like a champ. TY F150 online.

 

Just installed 4 new o-rings and my max a/c works perfect awesome info thanks alot for the help. 2.65 better than 600.00 bucks any day

 

I just used your write-up to rebuilt the EATC in my 2003 F 150 and it worked perfectly. Thanks for the great write-up.

 

After the dealer told me it would be $900 to fix the AC, I spent the last year plus, driving around with the only cool air coming out of the defrost.

YOU are the F'N MAN !!!!

Best write up ever !!

Played around looking for vacuum leaks for a while and couldn't find chit. All the lines around the battery and the one through the firewall were fine.


I took some pics along the way also, so i'll post them shortly !


Thank you, thank you THANK YOU !!!

 

Had the same problems and like SOP, checked this site before I did anything. Shop wanted to replace the whole unit (of course). Spent $3.44 on new o-rings and in about 30 minutes was blowing thru the vents again. AHhhhhhhh! G

Great write up. I hope lots of other people research this issue here before spending hundreds on a unnecessary replacement.

 

Reviving an old thread.

1st of all, thanks for posting this. I have found this site very useful (eg fixed my heated electric seats with info from here).

My 03 F150 Larriott EATC worked in all conditions except on floor setting. It would act the same as if it were in defrost setting and I was getting cold feet.
Thank you.

The reason for my posting, is that while pulling out the piston this morning to remove the last of 4 o-rings, it fell out onto the floor. I spent an hour looking for the spring and cannot find it. Does anyone know where I can get a spring?

I had to use the truck so I slapped everything back together and everything works, but I am not sure if the "auto" mode is directing the air flow to the right places. It seems to be the directing air to the same areas same as the "floor" mode.

Thanks!

 

Here is what I found out to answer my own question:
System Airflow Description — EATC:

When AUTO is selected:
The temperature control setting is manually set to the desired setting.
The air inlet door vacuum control motor is automatically controlled by the EATC module, based on the temperature setting.
The mode door vacuum control motors are automatically controlled by the EATC module, based on the temperature setting.
The A/C compressor is automatically controlled by the EATC module based on the temperature setting. The A/C compressor will not operate if the outside temperature is lower than approximately 6°C (43°F).
The blower motor is on. The blower motor speed is automatically controlled by the EATC module, based on the temperature setting, but can be manually overridden.

Looks like everything works without the missing spring. Hope AC works when it gets warm around here.

 

Just became a member. Wanted to say thank you to all who contributed to this great write up. This was a true time and money saver.
Thank you so much!!!!
John

 

Thanks so much for the info. on how to rebuild the EATC.
I was quoted $850 to replace. I found this thread, purchased the o-rings for less than $1, just installed and fixed the problem!

 

Devilsrighthand you made this job so easy!!!! I was done from start to finish in less than 45mins. You walked me thru this without a hitch. To have it fixed so easy and to save over a thousand bucks (cost me 92 cents) in the process is a home run. Thanks Steve

 

I did the O-ring swap yesterday and it did not work. When I had the EATC out, I plugged the two wiring plugs in and left the vacuum plug off. When I put my finger over the vacuum lines only one was pulling air (The black line). I followed the vacuum lines to a plug down by the gas pedal and only had suction at the same line there.

Is this normal operation?

Outside temp showed over 100 today in the driveway. {dying...gasp}

 

I tried and failed to do this. How important is the foam on the ends of each cylinder? Two of mine dienegrated when I pulled them apart. Very hot and very frustrated right now.

 

Ok round two found me success. I took them out and swapped a different size o ring...put it back in blows out of the vents. The floor doesn't seem to have much airflow but I rarely use that setting. Only issue it seems are the last two buttons on the right don't illuminate. Not a big issue for me at all...