HVAC System "Puffing"

[Johnboy]

I have a '13 FFH SE with the navigation/"infotainment" system. I've had a Ford service shop look at this issue twice now, and they claim it's by design. I'm calling BS.

 

The vent that blows from the top of the dash onto the windshield "puffs" gusts of air intermittently under the following conditions:

 

-Temperature set to 64 degrees +/- 2 (dual zone off)

-Fan speed set to 4 bars

-Airflow position set to Windshield plus the dash and/or floor

 

What happens is that the vent to the windshield opens for an instant, pushing a gust of air to the windshield, and then the vent closes. This happens anywhere from every few seconds to every few minutes on an arbitrary interval. Sometimes it only happens once or twice over the course of a half-hour drive. I'm told by the Ford service rep (who directly corresponded with a Ford engineer) that the windshield vent is what is used by the car's system to regulate the cabin temperature even when the system is not in auto mode. Apparently there is a temperature sensor which monitors the cabin temperature and works in conjunction with the windshield vent to regulate the cabin temperature.

 

This phenomenon is an annoyance and is either a malfunction (which I suspect is the case) or an indication of a poor design. Have any of you heard of this before, and if so, do you know of a cause/solution?

 

Thanks for your help!

[hybridbear]

I've never heard of using windshield and dash panel vents. Most cars will not allow this combination of vents. Perhaps that is why you're having issues. Typically windshield can only be combined with floor vents. And panel vents can be combined only with floor. Floor can be combined with either panel or windshield. And all 3 options can operate individually.

[inco]

It sounds like a pressure relief event with the pressure being built and then released. Is that even possible - no idea and not even sure how one would check that.

 

I was going to be sarcastic and say not to worry until the car starts "huffing and puffing", but I won't. Oh, I just did. Darn. :hysterical:

[Johnboy]

Hybridbear, does your car allow it? Without regard to what other cars can do, the buttons on my car indicate that it is allowed. Therefore, I would expect that it's by design, even if mine isn't performing it correctly.

 

I think we have pretty much the exact same car. Does yours do weird things like mine, with the system set as I described? I don't know if there's a correlation, but it seems to be malfunctioning most often when the outside temperature is cold (under 40ish degs F). But I don't know. Even in manual mode, it has a mind of its own.

[corncobs]

Yes the setting windshield + dash works just fine. I'm not sure about the puffing however it does make some weird noises once it starts blowing air.

[hybridbear]

Hybridbear, does your car allow it? Without regard to what other cars can do, the buttons on my car indicate that it is allowed. Therefore, I would expect that it's by design, even if mine isn't performing it correctly.

 

I think we have pretty much the exact same car. Does yours do weird things like mine, with the system set as I described? I don't know if there's a correlation, but it seems to be malfunctioning most often when the outside temperature is cold (under 40ish degs F). But I don't know. Even in manual mode, it has a mind of its own.

It will allow setting it that way, but I've never done it except when pressing buttons by accident. I'll try to remember to check it out this weekend for an extended period to see how it acts.

[acdii]

Perfectly normal in these cars. My 2010 did the same thing, and so does my 13. I think its due to lack of vacuum in the system, so a door falls open, and then closes when ICE kicks on to pull vacuum, or it could be just as described, the HVAC is automated even when not in auto mode. Somewhere in another thread is described the sensor in the window that helps regulate temps based on sunlight.