Defrost/heater help

S

SonnyZ4

Member
 Driver's Seat
Feel free to laugh at my question...but how the hell do you use the heater in the wintertime without it immediately fogging the windows?! Everytime I turn on the heater (with it set to blow half on the feet and half on the upper body), it blows air out of the defrost vents for a second or two completely fogging the windows. :headbang: It doesn't matter how long the car has been running, it always fogs and blows air out of the defrost vents for a little bit.

Is there a door thats not cutting of those vents? Is there some sort of ancient Chinese secret that I have to know to be able to use the heater without eliminating visibility?

It would be nice to not have to pull over on my way to work to let everything defog
 
I'm new to the Z4 myself, but with other cars, fogging would be quite common if I had used the air con on my previous drive - switching on the air con again would cure that reasonably quickly. I've always imagined that some condensation must be settling on the blower and then it is recirculated when you switch it on again.

If you found that the fogging didn't go, then you may have water somewhere in the cabin. Historically with other cars I had it in the footwell (Fiat Coupe Turbo heater matrix) and the glass panel leaking on a replacement roof (not OEM) for an S2000.
 
What you are seeing with the momentary defrost is the directional flaps "park" themselves when the car is shut off so they are in a known state at startup. There's no positional sensors per se, the system keeps track of position by counting motor steps. I suspect the flaps are rotating through the defrost position on their way to your selected position.

If you leave the direction partly on defrost and turn on the air con, the fog should clear fairly quickly unless the internal air is extremely humid. Once the humidity stabilises, you should be able to move the settings to your preference without consequence.
 
bcworkz said:
What you are seeing with the momentary defrost is the directional flaps "park" themselves when the car is shut off so they are in a known state at startup. There's no positional sensors per se, the system keeps track of position by counting motor steps. I suspect the flaps are rotating through the defrost position on their way to your selected position.

If you leave the direction partly on defrost and turn on the air con, the fog should clear fairly quickly unless the internal air is extremely humid. Once the humidity stabilises, you should be able to move the settings to your preference without consequence.
Click to expand...

It still blows through the defrost vents at the beginning even though I don't leave it set on defrost when I shut the car off. It's pretty much always set halfway between "feet" and "body".

I'll try the A/C with defrost next time.

Thanks again
 
I always leave my air con on - never knowingly had a problem. Have I been lucky and is there a problem around the corner?
 
I think you'll only have a misting issue if you switched it off during the winter as the ducts would condensate. But they'll do this each time you key off as it'll start to breed bacteria and smell.
 
Putter Whore said:
I always leave my air con on - never knowingly had a problem. Have I been lucky and is there a problem around the corner?
Click to expand...

It's the entire windshield, without any noticeable difference near the corners. I used to always use the A/C on low in the winter since I would be bundled up, but we've had relatively warm winter the past year so its only recently that I've started using the heater.

For whatever reason, today was the first time it didn't immediately fog up the windows when turning on the heater. But it still does blow out of the defrost vents when you turn on the heater regardless of where the vent knob was set when the car is shut off.
 
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