Model X HVAC poor defrost/defog function

Model X HVAC poor defrost/defog function

I live in NE Ohio where the heater/deicing is used a lot. On my 2017 Model X I have always had to manually turn on the defog function and have to continually play with it in fogging/icing conditions.

I got an Model S loaner that the defogging worked great. See the 2 screenshots. With the climate control on auto it would switch back and forth between 3 zone and defog only seamlessly.

My Model X has NEVER turned on all 3 zones or the defog only while in Auto. It stays on the lower 2 zones. The only way I get defogging is by manually activating defog next to the passenger seat heater icon. I pointed this out to the SC tech and tested my car and another Model X and said that the system is functioning as designed. Does everyone’s Model X require manually turning on the defog? The Climate control HVAC works great in the summer but is useless in Auto in the winter.


Vawlkus | 11 mars 2019

Not an issue in Canada. I’m sure we’d notice with our winters.

Redmiata98 | 14 mars 2019

I have always had to turn on the front/rear defrosters. They do not go on with “auto” selection.
Page 127 UserGuide
The windshield defroster distributes air flow to the windshield. Touch once to defog the windshield (the icon turns blue). Touch a second time to defrost the windshield (the icon turns red and the heating and fan operate at maximum levels). Touch a third time to turn off and restore the air distribution, heating, and fan to their previous settings.
5. Touch to warm up the rear window. When operating, the icon turns red. After 15 minutes, the rear window defroster automatically turns off. The exterior side mirrors are also heated whenever the rear window defroster is operating.
Page 129 user guide
Note: When air is directed to the foot-level vents, approximately one third of the air continues to flow to the windshield vents to assist in defogging. However, when air is directed to the face-level vents, air does not flow to the windshield because the air flowing through the face- level vents can assist in defogging the windshield.

bikeandsail | 15 mars 2019

Hi Redmiata98, Thanks for letting me know I am not the only one that cannot get defrost to work on Auto.

yraegel | 15 mars 2019

I am in Colorado so the humidity is low. The default setting for the front windshield defrost turns on the A/C and sets the temperature and fan speed to high. I can turn off the A/C but as soon as I decrease the temperature and/or fan speed, I start getting fog on the side windows and eventually the front windshield. So I turn back on "grab a beach towel and put on your bathing suit" mode. I've only had this in temperatures below freezing. A/C with the defrost setting actually fogs up everything here in certain conditions like a cool rain. A better way to set things quickly and not have to bake yourself just to see would be nice.

bikeandsail | 18 mars 2019

Hi yraegel,

The first time you hit the defog it should only redirect the air to the windshield. The second time, in close sequence, should do as you describe. Third time reverts to auto or if you push only once a wait a bit second push will revert to auto.


jjgunn | 19 mars 2019

Software always seems to point the fan through the defroster windshield vents.

Also...crank up the temp to "HI" when turning on via the app

COrich | 20 mars 2019

Turn off recirc. It is on by default when the outside temp is too low. With recirc off, defrost works fine.