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Defogging Windshield

Defogging Windshield

I've had my M3 for 8 months and love everything about it except the fact that I seem to have a great deal of trouble getting the front windshield (and driver/passenger windows too) cleared in the mornings in very humid conditions. I have a 40 minute drive into work in the DC area and as I get about halfway to work the windows will often start to fog up and continue to get to the point where I constantly need to turn on the windshield wipers to be able to see (and this doesn't do that great of a job). I have tried every variation on the climate control settings (standard AC vs the defogger/defroster button, recirculated vs outside air, vent positions, etc.) and nothing seems to work. Does anyone have any suggestions or have you had similar issues?

Idahorefugee | 14. august 2019

You mention that you've tried all the things I'd normally suggest, so I'll give you my last thought (which is a long shot). Is the condensation on the inside or outside of your windshield? I've noticed that if I run the AC too long in defrost mode, the windshield gets cold enough to make water vapor condense into liquid on the outside (easiest way to check is to give the wipers one swipe). The solution is to turn off the defroster for awhile or turn up the temperature.

You could also try using the defrost "button" on the main screen, it has 3 settings (off, hot and cold). It overrides the current climate control settings to go into maximum defrost mode. If this helps with your fogging it should at least give you hope and a hint on setting the climate control manually.

AWDTesla | 14. august 2019

I have it on recirc and it gets rid of the issue of having to use my wipers.

Techy James | 14. august 2019

Question, are you using AC (Defrost Blue Icon) or Warm (Defrost Icon Orange)? Sounds like the condensation is actually outside the car not inside if tapping wiper button clears it up. This indicates the temperature inside of window is cold enough to have same effect ice in a cup has sitting in room temperature room. This condition is not unique to Tesla, but any car if your running AC defrost mode to try and clear front window.
So first thing to try and fix depending on temp, turn off defrost mode and set internal car temp close to outside temp. Another thing you could possibly do is hit the defrost mode second time to switch from AC ran Defrost to Heat Defrost. Note here using defrost mode bypasses auto climate control on temp so car can get colder or warmer depending on defrost setting than would if using set temp on climate control Auto Mode.

SteveWin1 | 14. august 2019

I have the same issue in Florida. Its hot and humid. Obviously I want the inside of the car to be cool and dry, so I run the AC. When the windshield gets cool, the warm humid air on the outside of the car fogs up the windows and I have to run the wipers, which helps enough for me to get by, but isn't that great.

This does not happen in my F150 in the exact same weather. Maybe its because the Model 3's windshield is closer to the hot (usually wet) roads?

coleAK | 14. august 2019

Different climate but same issue. Have you tried just setting it to Auto? I’ve never really used the auto climate setting on any of our previous cars but in the Tesla it pretty much eliminated fogging.

richtrav | 14. august 2019

Had this bad a few days ago, apparently a small critter had crawled up into the front wheel well and died so I was trying to get rid of the stench in the car. The fogging was worst when I had recirculate on, air vents set to come out at the dash, and the temperature too low. The worst offense was setting the vents to dash, it cools the windshield glass well below the dew point temperature outside which causes the fog. Tapping the front defroster twice so it turns red will heat the glass enough to evaporate the dew but puts out too much warm air to be comfortable for any period.

This seems to be an issue with electric cars in general, the i3 fogs up pretty easily too.