Solved Air conditioning goes to defrost when accelerating, then returns.

[oaxaca_one]

I have a 2008 Explorer. When I accelerate, the air conditioning airflow completely disappears from the front vents and switches to coming out the windshield vents (like defrost). When I ease off the accelerator, the air flow returns to the main vents.

This never happened before a local mechanic cleaned out my cabin air vents (I wasn't getting much airflow, now after the clean I get strong air).

Any ideas??

Thanks in advance.
--Greg

 

[2006GrayXLT]

Well on my 250 there was a vacuum leak behind the dash. Not sure if that's an issue with your explorer.

 

[Rcflyer330]

Check the one way ac check valve in the engine bay for the vacuum reservoir. usually when they go bad you will a hiss in the passenger side foot well when accelerating. If you do a search on the fourm you will find quite a few threads on the problem. I read somewhere that when the system looses vacuum the default position is defrost.

 

[rmcalis]

I had same symptoms on my 2010, replacing the one way check valve did the trick.

 

[gdgiordano]

A/C only blows thru Defroster Vents

Go to the final few posts in this thread. I am certain it’s your check valve. I had the same thing. I just did mine.

 

[MAS Tequila]

You definitely have a lack of vacuum while accelerating.

Before replacing anything, check the line going from below the blower to the vacuum ball.

They like to chafe and leak.

 

[oaxaca_one]

usually when they go bad you will a hiss in the passenger side foot well when accelerating.

Now that you mention it, I did notice a hiss (not loud but I could hear it) coming from the passenger side when I accelerated. I'll bet the check valve is the problem.

Thanks for the reply.
--Greg

 

[oaxaca_one]

Just an update...

You were all right. It was the A/C one-way check valve. I got that replaced and all the problems have gone away.

I live in Mexico, and so the part + labor cost me $11 bucks! I'll take that any day.

Thanks to all.
--Greg

 

[Rcflyer330]

Good to hear you got it fixed.

 

[BrooklynBay]

Thanks for the update. Your thread is marked as solved.

 

[gdgiordano]

Awesome! Best $10 part ever.

 

[Josh C.]

Does anyone happen to have the part number of the check valve?

 

[swshawaii]

^ Motorcraft YG-360

A/C only blows thru Defroster Vents

My 02 Explorer Limited 4.6 started doing this a few weeks ago, but got real bad yesterday. Mine only does it under load, above 40 mph. Driving in town it never does it, but as soon as I get on the highway and gun it she starts to act up. A/C goes from the dash vents to the defrost vents. It was...

www.explorerforum.com

May be only used on 2002-10.

 

[94Eddie]

Does anyone happen to have the part number of the check valve?

Amazon product ASIN B000NU8FFY

 

[Josh C.]

I'm a dumbass, I didnt even look to see that this was a 3rd Gen thread