Air blowing through defogger vents when climate set to floor only?

[User100723]

So I’ve been beating it over 95f lately during my commutes, and sometimes prefer to keep the climate set to floor only to reduce chances of eye/nasal irritation during a drive. What I’ve noticed is in doing so, my windshield and front windows begin to fog up horribly fast, to the point where I lose all visibility unless I use the wipers and roll the windows down and up again.

This morning, I realized why this is happening: anytime I set the climate to feet only, air starts being pushed up and out of the defogger vents as well. Once I turn on the front-facing vents, air stops flowing through the defogger vents. But as soon as I switch off the front vents and set things to feet only, air starts coming up out of the defogger vents as well, even though the defogger settings are all off.

Is this normal/expected behavior? Anyone experience this with their Mustang Mach E, where air comes up through the defogger vents in addition to the floor vents, even though the defogger option is turned off?

edit: thanks for the replies and suggestions everyone, so apparently this is normal and I just have to adapt by avoiding the feet only option entirely, and switch to using both feet and front facing vents to get around the mandated feet/defogger config, and keep the front facing vents closed when I don’t want it blowing air around my face. And I’m not disappointed with the cooling (or heating) of the car at all, especially considering the numerous early posts from others worried temperature management due to the glass roof. It keeps me sufficiently chilly or toasty when I need it during my commutes. Unless my so of course turns everything off due to personal temperature differences, then I might have a problem ?!

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[bshaw]

Just leave it on auto mode and point the vents away from your face. The air conditioning is more than adequate to keep this car cool at 95f. Recommend you remote start climate control about 5 mins before getting in the car, and it won’t be blasting by the time you enter.

 

[Mach-Lee]

Yes, there is a small amount of airflow to the windshield in floor mode by design.

I strongly recommend you use the AUTO mode, simply adjust the vents to not blow in your face. A/C does not perform well blowing from floor vents, you must use the panel vents to get effective cooling. Also remember the air coming out of the vents is filtered.

 

[User100723]

Thanks for the confirmation, yeah I already have the temperature, remote start and all that set, but there are times when I need to have the car rapidly cooled down during a drive as it helps to get me a little chilly before I work long hours in high heat and humidity. Ah well, another irk I guess. Appreciate all the tips though, especially the one about closing the front vents. Can’t believe I forgot I can do that! (I tend to set and forget about the vents on the first day of driving, just like the seats and mirrors).

 

[TheVirtualTim]

It’s a requirement that cars do this. It’s really designed around winter weather … so that when you run the heater to the floor vents there is always some air blowing up through the defrost vents to keep the window clear.

There are numerous requirements around the defroster — NHTSA considers it to be an essential part of the car … so many of these design decisions are imposed indirectly through NHTSA requirements. This is why, for example, you’ll notice a defrost switch next to the headlight controls … even though there’s a defrost control on the center screen. (The switch is there in case the center screen dies … you must be able to clear the windshield to be able to see before driving the car.).

Tesla also used the center screen to activate the defrost, but didn’t have a backup should the screen fail. Tesla center-screens started failing (really the software failed) when a memory card failed due to excessive ‘write’ operations after years of use (Tesla saved logs to that card). It was an expensive fix (which should have been a cheap fix) and Tesla expected drivers to pay for the repair. NHTSA forced Tesla to repair it for free as they found it to be a safety defect — entirely because that meant there was no other way to defrost the windshield. That was an expensive lesson for Tesla.

 

[User100723]

It’s a requirement that cars do this. It’s really designed around winter weather … so that when you run the heater to the floor vents there is always some air blowing up through the defrost vents to keep the window clear.

There are numerous requirements around the defroster — NHTSA considers it to be an essential part of the car … so many of these design decisions are imposed indirectly through NHTSA requirements. This is why, for example, you’ll notice a defrost switch next to the headlight controls … even though there’s a defrost control on the center screen. (The switch is there in case the center screen dies … you must be able to clear the windshield to be able to see before driving the car.).

Tesla also used the center screen to activate the defrost, but didn’t have a backup should the screen fail. Tesla center-screens started failing (really the software failed) when a memory card failed due to excessive ‘write’ operations after years of use (Tesla saved logs to that card). It was an expensive fix (which should have been a cheap fix) and Tesla expected drivers to pay for the repair. NHTSA forced Tesla to repair it for free as they found it to be a safety defect — entirely because that meant there was no other way to defrost the windshield. That was an expensive lesson for Tesla.

Thanks for the detailed write up, yeah it’s never been a problem during winter, only summer. And I’m very glad our cars do have physical buttons for certain critical features such as what you’ve mentioned. Still kinda irks me that the defogger systems appears, though functioning as intended, actually does the opposite of what it’s supposed to do when you run the AC to feet only during the heatwave seasons. I’m sure other manufacturers have implemented this in a more advanced way so as to not fog up the windows during summer season, but I guess I’ll just have to remember to turn the front facing switch on and close the vents for in my side as others have mentioned.

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