HVAC airflow changes during acceleration/hillclimb

[stranger706]

2010 with auto a/c and rear a/c.

Sitting still, and during cruise conditions, the system works great.

While accelerating or going up a hill, the air will start blowing through the windshield defrost vents. It does not matter if the air flow is set on floor or dash, it will just change and start blowing through the windshield vents. Once up to speed or over the hill, it will switch back to where its supposed to be.

Also during acceleration there is an air hissing sound coming from the passenger dash area.

The 2 issues seem to be unrelated. They usually don't happen at the same time, but sometimes they do.

Is this anything I can fix myself? I have no faith in dealerships, they will just kick the tires and give it back to me.

Thanks,
PJ

 

[A Wise Guy]

Let them find the vacuum leak. If you have a '10 it should be under warranty, let them make it right.

 

[bender]

I've been dealing with this in my 08 for over a year with 3 unsuccessful attempts by the dealer to fix. this is the part they've replaced #1L2Z 19D611 AA I still have the issue and my bumper to bumper runs out today.

it is a vacuum leak of some sort and the reason it goes to the defrost is that is the default setting when the vacuum pressure gets low. very annoying and frustrating (sorry). I would give your dealer a chance to track it down. I don't think the part above is the problem, I think it is just intermitant and they guess.

good luck.

 

[Joe Dirt]

Bender- if you have record of the repair being started before warranty end, you should be able to have it completed. Make sure they acknowledge that, and make sure they note original date and mileage on the work orders just in case something happens and you need documentation.

 

[A Wise Guy]

I've been dealing with this in my 08 for over a year with 3 unsuccessful attempts by the dealer to fix. this is the part they've replaced #1L2Z 19D611 AA I still have the issue and my bumper to bumper runs out today.

it is a vacuum leak of some sort and the reason it goes to the defrost is that is the default setting when the vacuum pressure gets low. very annoying and frustrating (sorry). I would give your dealer a chance to track it down. I don't think the part above is the problem, I think it is just intermitant and they guess.

good luck.

Bender you may also want to contact a new member that goes by the name fordcustserv. As his name implies that is his job.

 

[chapsdeva]

I have had the same issue with a vaccum leak/hissing sound on my 08. First time, dealer replaced the AC check valve. That solved the problem for two months and then it came back...although not as bad. Replaced the same part again along with the vacuum canister. Just got the truck back last week and so far all is good..........for now! Truck is about to turn 30K and if it happens again, I'm raising holy hell with Ford.

 

[chapsdeva]

Noise is back...the check valve is these trucks is pure junk. As much as I want to go in and raise holy hell with Ford, I'm going to spend the $15 bucks or so and get a new one if I can't clean the existing one. The truck is out of warrenty and I don't feel like messing with Ford over a cheap fix I can do myself...still pissed though!!

 

[Jamesemud]

Noise is back...the check valve is these trucks is pure junk. As much as I want to go in and raise holy hell with Ford, I'm going to spend the $15 bucks or so and get a new one if I can't clean the existing one. The truck is out of warrenty and I don't feel like messing with Ford over a cheap fix I can do myself...still pissed though!!

Did you ever get this resolved? I am having the same issue. Where is this "check valve located?
Thanks

 

[Fordman6996]

I have a 2008 limited with the 4.0L v6 and I'm having a similar issue.. when ever I accelerate or when it does a hill climb while going down the high way the AC blowing from the vents seems to not come out as much untill the RPM's drop after the hill climb then it blows out the vents normally. I don't hear the fan speed change just not as much cold air is coming from the vents.. I would also like to know where the AC check valve is located and the Vacuum canister.

 

[HoustonTexan]

I have a 2010 with the air conditioning going off under load. I hear the hiss then a thump that sounds like it is from the passenger side. Where is this check valve? I dont see it under the dash. Any pics? I am sure it is a vacuum leak but dont know where!

 

[hcroker]

Can anyone tell me where the check valve is? Same issue on my 07 XLT. Not a world-changing problem, but irritating.

 

[polizi212]

Can anyone tell me where the check valve is? Same issue on my 07 XLT. Not a world-changing problem, but irritating.

its on the fire wall, under the hood and on the left side of the engine compartment. i will take a photo in the morning and post it to show you!

 

[polizi212]

the check valve is located at the tip of the arrow in the picture, keep in mind it may be behind the air conditioner lines, so you will have to look for it but it is there!

 

[jschilberg]

Found what my problem likely was, although I still need to do a test drive. I replaced the plugs in my 2010 Explorer Limited 4.6 V8 a couple weeks ago and inadvertently knocked loose a vacuum fitting from the top of what looks like a vacuum operated heater hose valve (located on passenger side of engine).

I'm almost 100% certain this was the culprit of my AC blower shutting down during even the slightest acceleration. I'll confirm later in the week.

4-28-14 Update - That was it! The blower and AC functioned perfectly during my drive to work. I have a couple pics that highlight the fitting I accidentally disconnected during my spark plug change. PM me if you'd like to receive them via email.