Hey guys,
I turned my A/C on for the first time yesterday, since last fall, and It will not blow thru the panel vents. It work great last year. When I turn it to either A/C or Max A/C it blows thru the defroster vents. All the other settings work great. Someone told me that it could be a possible vacuum leak, but where? Any suggestions. Thanks

 

Click on SEARCH and enter "+defrost +vacuum" for previous discussions of this FAQ.

Steve

 

IT IS THE E.A.T.C. I had it go out on my 03, its stands for the Eletric Automatic Temp Control, the dealership said the part was like $500.00 bucks. I think that you can get it at advance auto parts for around $250. Not to sure, I called and they said that was the part but some one else told me that it was only a dealer part but good luck with it.

 

Possible but particularly likely.

Follow above directions first. You might save yourself up to $500.

Steve

 

Should have read:

"Possible but NOT particularly likely."

 

check vacuum lines under hood by the firewall

 

I just saw this thread when I got home Last night. I have the same symptoms with my 03 F150 Lariat 4x4 with EATC. It has been working fine then just started blowing through the defrost registers, actually it will just shift back and forth between dash vents and defrost registers without the engine demand changing. So, I looked for suspect vacuum leaks in the areas discussed in the various other threads, no evidence at present that the vacuum line is leaking but it sure seems like it. I also saw a thread about initiating a diagnostic on the EATC system via the control head. I was able to get into the diagnostic mode but the EATC reported no codes. After coming out of the diagnostic mode I ran my AC and the vents just continued to blow air for about 10 min did not switch to defrost vents. Wonder if the EATC could have been confused and doing a diagnostic reset it. Sure wish I had schematic of all the vacuum lines. especially the ones going to the solenoids on the firewall.

 

Any further Info on this?

I assumed a vacuum problem as well but have not found anything that could cause this. I am having the same problems.

I am assuming its the EATC as well, and I am worried what this might cost since I have not been able to find this outside of a Ford Dealership.

Thanks

 

DaveFL, I'm pretty sure I narrowed mine down to the EATC head/display on the Dash.
The reason I say this is, I checked Vac lines from manifold to reservoir all seems good. Checked check valve, good. disconnected plastic supply line going into cab with my mightyvac pulled a couple units of vac doesn't take much. Made sure a/c was all off nothing running and display blank. Had buddy turn on vehicle. then he hit the VENT, switch and I watched vacuum gage go to zero. This suggested a leak, either on head or at actuator or line from head to actuator. removed supply line to actuator for distribution door (red plastic tube) with engine running and supply reconnected and VENT selected very little vacuum not enough to open door.
connected small tygon tubing to inlet port on actuator conected mightyvac and pulled a couple units of vacuum VENTS blasted full air.

Going to pull head out this week to see if I can validate Line (red) from head to door actuator, if they line is good then it's the control head. Then I'm going to rip into it to see how it is made maybe I can fix it.

New EATC head cost 567.00 from dealer online 482.00 from a salvage yard, anywhere from 265.00 to 40.00 bucks So, if it is the head some micro surgery might fix it gotta see what kind of valve is in the control.

I'll post an update and some pictures as well. It's a shame that the link for the vacuum diagram does not work for me would have saved a few steps.

(link takes me to page says ready to download just starts a few Kb then stops. guess it wants me to join.)

MightyVac is a very good tool for this job see if you can borrow one.

 

Although I havent been as through a you Im pretty sure its the unit itself as well. Was going to do a more detailed check this weekend.

With that said and not sure if you need a new one or what, but I contacted a Ford Dealership near me in FLorida who I have had great luck with parts in the past.

Santa Fe Ford in Alachua Florida.

He quoted me 420.00 for the unit.

I have had bad luck with electronic salvage parts in the past so unless its cheap or comes with some kind of warranty I won't go that route.

Good luck let me know what you find and I will let you know what I find as well.

Dave

 

03 F150 4x4 Screw 118Kmi

Same problem with a/c blowing thru defrost for last month or so. I have noticed that mine will shift to defrost under acceleration and panel in coast or decel.

Checked vacuum and no leaks.

EATC....is that the little round plastic thing in the center of the dash? Is that what you are going to pull??

 

Nope the EATC is the control unit for HVAC controls, basically the Head unit for your A/C system.

 

Is that where the black vacuum line that goes thru the firewall terminates?

 

Well guys after messin around with my issue, today I found out that one of the plugs on the back of the crontrols was not plugged in all the way. Plugged it in and now it works great.

 

I have a 02 super crew and am having the same problem. Mine goes back and forth between the panel and defrost also. Mine doesn't seem to change with speed or throttle. Letsgowheelin: When you say that a plug was loose, was that on the back of the head unit? Any pictures?

Thanks in advance....

ebman74