Why is this happening??

[Blackened300a]

For the past 5 days, Everytime I turn on My A/C It Will Blow out the dashboard Vents then stop and start Blowing out the Defrost Vents!! I turn it Off then back on and it will work through the vents for a little while then go through the defrost Vents on its own. If I turn the A/C on Norm and keep the fan low, It will work fine until I go Full Throttle, then it go out the Defrost Vents once again! I was driving on the highway today, the A/C was blowing through the Dash Vents and I noticed that when I give it a little throttle, the A/C wouldnt blow out as much, then when I Let off the gas it will Start Blowing normally. Now Im aware that it has something to do with the Vacuum. But Im Not sure if any of my Mods may be the cause of it. I have installed the PHP Airbox and the PHP Intake Spacer. I have also installed a SCT tune From DR. I wonder if this would create a vacuum problem?? I have Checked all the vacuum lines coming off the Intake Cover As well as following the Vacuum diagram and checked all the hoses. I dont see any leaks or cracks in any of them so Im Puzzled. Before I make a trek to the Dealer, I want to be sure that It wasnt My Mods that cause this. Any Help is appriciated

[bigjohn]

Definitely the signs of a vacuum problem. I've had a number of Fords over the years do this. Since I've only had my MM for a few days I can't begin to tell you where to look. But the way Ford's HVAC controls usually work, no vacuum sends airflow to the defroster outlets. At WOT there is little to no vacuum. When you let off, vacuum returns and your system returns to normal.

There is usually a vacuum resorvoir (the ones I've seen are about coffee can sized) with a check valve on it to supply the HVAC controls with vacuum during WOT so this doesn't happen. Not sure where it is on these cars but it sounds like yours may not be working properly.

[Blackened300a]

Thank you Very Much, I shall try to hunt for the canister. Anything to save me from leaving my car laid up at the dealer.

[Smokie]

Think back to just before 5 days ago, did you do anything under the dash? You may have disconnected a vacuum line, same question for under the hood, any work prior to 5 days ago? There may be nothing broken, just something disconnected.:)

[fastblackmerc]

Think back to just before 5 days ago, did you do anything under the dash? You may have disconnected a vacuum line, same question for under the hood, any work prior to 5 days ago? There may be nothing broken, just something disconnected.:)
Yep, it's a vacume leak.

[MENINBLK]

The Vaccuum Canister is on the Driver's Fender liner.
It looks like a component cause it's square, but it has a hose connected to it.
If it is cracked, or the hose is disconnected, then that is the reason
why your vents are acting up.

[ckadiddle]

You guys are way off base with "vacuum leak". It's one of these reasons:
1. Alien abduction of the Marauder to probe it's inner workings.
2. Sunspots.
3. Gamma Rays.
4. Parked too close to a Honda and was affected adversely by Evil Ricer Energy Field.

[CBT]

You guys are way off base with "vacuum leak". It's one of these reasons:
1. Alien abduction of the Marauder to probe it's inner workings.
2. Sunspots.
3. Gamma Rays.
4. Parked too close to a Honda and was affected adversely by Evil Ricer Energy Field.Just when I thought it was safe to take off my aluminum foil hat!

[Blackened300a]

Thank you Very Much for the Tidbits of Info, I dont think the List of 4 Possible reasons would qualify as Help but it was funny lol

[scareme]

I've been having the same issue and can't find anything disconnected anywhere. Please keep posted if you find the problem, I've actually given up on it since it does work after a little driving for whatever weird reason.

[Blackened300a]

I've been having the same issue and can't find anything disconnected anywhere. Please keep posted if you find the problem, I've actually given up on it since it does work after a little driving for whatever weird reason.
Yeah I will keep you posted. I plan to go through all the vacuum lines and the canister to make sure there is nothing cracked or leaking, then Im off to the dealer for a controller probably. Have you Tried Putting on the Vents, then Switch to the Defrost, then Switch to the Vents again??? On my Car it stays on Defrost and dont switch back to the vents even at idle. I been putting up with it since Its coming out the vents and I have some AC at the time but I do plan to get to the bottom of it Very Soon

[scareme]

Mine won't change do to me playing, only when it feels like it. Once it starts to work it's like nothing is wrong. Usually starts after a few miles of driving???

[Sinister]

When it stops blowing out dash, I figured out that you can turn fan all the way down and when air starts blowing out dash vents again, you can sneak it back up. Sometimes.

[Marauderjack]

HVAC controller......Just had mine replaced for the very same reasons!!:argue:

Out of warranty it is over $400......Luckily mine is still a warranty fix.....took me all of 10 minutes to pop it in!!:beer: My dealer likes for me to do things like this as in keeps me out of the shop!!:cool:

Marauderjack:burnout:

[Blackened300a]

Nothing like Following up over a year later. I went to the dealer and it was the electric heater control. Basically the dashboard temperature control unit.
Has been perfect since.

I forgot I even started this thread, I started reading it like it was new until I saw my avatar

[Drock96Marquis]

FYI, when set to "Auto", the EATC WILL switch between air outlets as it sees fit. It will change fan speed, temperature and airflow outlet THROUGHOUT the driving cycle, making changes as needed.

Don't believe me, read your owner's manuals.


Also, for anyone curious here is a pic of the EATC vacuum setup:
http://www.p71interceptor.com/eatcswap/schematics/eatc/eatcvacuum.gif
--Image Courtesy 2vmodular

[Marauderjack]

The only time mine searched all over the place was when the "EATC" was bad!!:argue:

When it is 95* here and the inside of the car is 125* it now simply goes right to recirculate (MAX) out of the dash vents only!!:beer:

Before, with the bad one, it would go to Defrost.....Floor.....Defrost. ...Floor over and over!!:cool: After it cooled a bit and the fan speed was reduced it would send some air out the dash vents and a lot out the Floor and Defrost vents??:( Eventually when the fan went to low speed most would come out the dash......Not at all the way it has worked for 2+ years!!:shake:

New module and it is back to NORMAL!!:D

I was more worried about screwing up the vacuum controlled doors since they were in constant motion!!:eek:

Marauderjack:burnout:

[rkk]

I've been hearing about EATC and HVAC issues on this thread.

Now, I have the symptoms where Max A/C air comes out the defrost ports for about 2 miles before correctly emitting out the dash vents.

Marauderjack said the HVAC unit is $400 if out of warranty. Are these terms interchangeable or separate components? Also if different, how much for an EATC?

[RF Overlord]

EATC= Electronic Automatic Temperature Control

HVAC= Heating Ventilation and Air Conditioning

HVAC is a generic term...

[miamisilvermm]

Well i just encountered the same problem. I knew I'd find some info here. How much did the repair cost?

[Blackened300a]

Well i just encountered the same problem. I knew I'd find some info here. How much did the repair cost?

Dealership covered everything under warranty. If I remember right it would have ran me over $500 for the parts and labor.

[MENINBLK]

I am having a similiar problem.
When I am accelerating *slightly* as in changing to the passing lane
and accelerating for another 5 - 10 MPH, the airflow will go to the
defroster ducts after 15 seconds or so.
When I settle at a speed, or take my foot off the accelerator
the airflow returns to the center dash outlets.

This also happens when the Cruise Control accelerates to adjust speed.

I know what you guys are saying but this IS a vacuum problem.
Either there is a vaccuum sensor in the E-HVAC controller that goes bad,
or there is a vacuum leak somewhere between the intake and the
vent actuators.

I am going to get a can of ether and look for this leak.

If it isn't a leak, then the vacuum check valve on the IP vacuum line has to be bad.

[rkk]

MENINBLK, keep us posted.

I've noticed a few things about mine lately. It usually acts up more prevalently on short trips. If I only drive about 3 to 5 miles and shut the car off, it seems when I start it up again to blow out the defrost ports for about 2 miles of driving before correcting itself. If I drive about 25 to 50 miles and shut it off, then when I start it back up again it works fine from the get go.

I have not experienced a change in air flow due to the cruise control device.

[MENINBLK]

I finally figured out how to reset the EATC.
I did it and the electronics are checking out okay
but they aren't working right.

I unscrewed the EATC from my dash and held it in my hand
while I brake revved the engine to 2000 rpm.
Within 15 sec, I could feel the vacuum solenoids switch and divert
the airflow to the defroster.

I dont' know why it is doing this, but it is.
I am going to put a vacuum gauge on the engine and test this again
to see if I am actually losing vacuum.

I did notice that there is a check valve on the line
that goes through the firewall.
If the check valve is bad, I can just put another one inline
on the black vacuum line that feeds the EATC.

If the EATC reads vacuum, which it might, and the check valve is leaking,
then the solution may be to only replace the check valve.

Does anyone know if the check valve is available,
or where someone can get one ?

[RF Overlord]

MIB, did you ever resolve your issue? While at MVV, I discovered that my new (to me) Silver Birch is doing the exact same thing as yours.

[Richy04]

For those of you having vacuum leaks right at the control head, try vaseline or a thick silicone spray first on those parts. The seal is dependent on how soft the rubber parts are and how well they are lubricated. After 4-5 years of use these coatings wear off and may cause vacuum leaks. Fords always used a vacuum can and servos to operate the vent controls. There is usually a one way check valve which prevents leak down from the canister.

Usually a few shots of a good thick silicone spray like permatex brand into the lines, servos, bladders and controls and then working the controls thru each setting may settle things back down to normal. It will work providing that there is no vacuum leaks in the system.

Do not get silicone spray on any plastics, some will discolor black or dark plastics, some wont though..

[Big House]

Having the same problem....

[merc]

I finally figured out how to reset the EATC.
I did it and the electronics are checking out okay
but they aren't working right.

I unscrewed the EATC from my dash and held it in my hand
while I brake revved the engine to 2000 rpm.
Within 15 sec, I could feel the vacuum solenoids switch and divert
the airflow to the defroster.

I dont' know why it is doing this, but it is.
I am going to put a vacuum gauge on the engine and test this again
to see if I am actually losing vacuum.

I did notice that there is a check valve on the line
that goes through the firewall.
If the check valve is bad, I can just put another one inline
on the black vacuum line that feeds the EATC.

If the EATC reads vacuum, which it might, and the check valve is leaking,
then the solution may be to only replace the check valve.

Does anyone know if the check valve is available,
or where someone can get one ?

The check value is 20 dollars from Ford. I had them order one for me but didn't need it.

[Richy04]

Sounds more like dry check valves and unlubed manifold parts (these are the parts which route the vacuum to the servos in the EATC). I'm telling you guys, give it a spritz, the check valve will not work without a lubed seat causing the vacuum to be limited to what is in the lines only.

Take the time to spray each line you can find and especially the check valve and lines in and out of the EATC, this should solve most if not all of the dryness related leaks..

The accumulator will only "store vacuum" if the check valve works. Try it, you will be pleasantly surprised.

[ctrlraven]

I just started having this problem also a few weeks ago, I notice when it's really hot out 85 or above is when it acts up. Had to deal with it the whole time while at MMV. I'm going to try to get it to the dealership soon since I only have 13-14K miles left of my warranty.

[Jon01]

Good response Richy, I didn't think about doing that when I was having the same problem. But replacing the EATC did fix the issue...I'd be curious the impact that would have though. Sure beats shelling out $400+!
Those not covered by warranty who are replacing it, there's NO reason to pay the dealer's labor for it, takes maybe 10 minutes to change. Just pop the dash trim off, 4 screws, disconnect old one and reverse your steps.

[Richy04]

If anyone had an MM- EATC or any illuminated or non-illuminated switches (seat warmers,window, seat, etc..)that they've swapped out, let me know if you want to sell the defective parts. I am looking for these to start repairing them as it seems that all of this stuff will be a headache to find one day.

Tnx Richy