Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register
  • We just completed a significant update, but we still have some fixes and adjustments to make. Please see this thread for more details and to find out how to revert to the old design. Cheers!

Proper HVAC setting to prevent outside windshield condensation in humid conditions?

ajs847

Member
Jun 2, 2021
678
2,187
northwest illinois
Let me paint a picture for you: MYLR parked in garage, I unplug from the WC and right before we start driving the tesla app shows interior temp 72, exterior 73 before getting in. Actual outside temp was 70 degrees.

Wife and I have a 20 minute drive to dinner with friends. Here in the Chicago area we have a rain system pushing in from the West with a ton of humidity in it's midst. (98% humidity at the moment) The rain hasn't started yet but humidity was in the 90% range.

So we start driving with my typical HVAC setting since getting my Model Y in early Sept has been 65 degrees with fan at speed of 3. Never experienced windshield fogging keeping all else constant (never turned on or off recirculation) - but it came on from the SC where I picked it up so i decided to leave it on - if that makes a difference to anyone? never used auto and never had to use the defrosters until tonight. Fan's pointed at us.

So we barely get 5 minutes out of our neighborhood and I'm hitting the wiper button every 30 seconds - 1 minute to clear up condensation that is causing visibility issues for me. I hit the defroster button and it starts to get worse. What gives?

At this point my wife is asking WTF is going on, what is this janky POS you got me driving around in. I had to pull over and park to look at the HVAC settings to see what is going on, still couldn't figure it out. I suspect that maybe recirculating the air was causing the issue but at the time with my wife reaming me out, I didn't think to turn it off.

I never had these issues in my previous BMW's. I'd crank the AC low, throw on the defroster without recirculating air and in these types of conditions I had the muscle memory dialied in that I could make all these adjustments while driving and keeping my eyes on the road.

So, what would your preferred HVAC settings be in the conditions I described.
 
Upvote 0

jcanoe

Active Member
Oct 2, 2020
3,868
3,953
Maryland
The Tesla HVAC system works best in Auto as it can automatically adjust the fan speed, air flow and will regulate the cabin humidity as required to keep the windshield from fogging. In high humidity or rain leave the Recirculate Cabin Air HVAC setting set to OFF as this will trap moisture inside the cabin.

Once moisture condenses on the glass there are two ways to go; either lower the cabin temperature below the temperature of the glass (to eliminate fogging in the inside) or turn on the defroster to warm the glass to stop moisture from condensing on the inside and outside of the glass. Try increasing the set cabin temperature from 68F to 70F or 71F.

I usually keep the temperature set between 70F and 71F and have no issues with fogging on the inside. There are times, usually in the evening, where condensation settles on the outside of my Model Y while parked. In those cases I use the windshield wipers to clear the windshield and the rear defroster to clear the rear glass.

Perhaps if you unsync the dual zone climate control, set one temperature for you and a lower or higher temperature for your passenger this may reduce the amount of condensation on the windows.

To clear the condensation forming outside the vehicle on the glass run the windshield wipers on the lowest setting and turn on the rear defroster.

The Tesla Voice Commands can be used to control the windshield wipers, Recirculate Cabin Air and other HVAC settings.

"Set wipers to Low/Medium/High" or "Set wipers to 1/2/3/4/Off/Auto"

"Recirculate Cabin Air" and "Fresh Air"

"I'm Cold" raises the cabin temperature by 3 degrees, "I'm hot" lowers the cabin temperature by 3 degrees.

The windshield defroster has two settings. If you tap the windshield defroster icon once it turns blue and will direct cooled air to the windshield to defog the windshield. If you tap the windshield defroster icon twice it turns red, sets the temperature to Hi and directs heated air to the windshield. When you turn on the windshield defogger/defroster and it is cold outside the side mirror heating elements will activate.
 
EVERY modern car since about the early 90s with AUTO hvac works best and most efficiently with the hvac set to AUTO! I am always baffled when people use manual settings with a car equipped with AUTO hvac.

I have had easily 25 cars since 1990, and I have used AUTO 70F in EVERY car in all weather from -25 to 122F and AUTO 70F has worked flawlessly...even with torrential humidity.
 
  • Like
Reactions: RoBoRaT and Redekw

Pianewman

Active Member
Oct 28, 2020
1,560
1,129
Fort Worth
Condensation on the windshield under high humidity seems to be normal around here, for my Toyotas and now the Tesla. The first 4-5 minutes of early morning driving requires windshield wiper use, until the windshield gets to a certain temp, I guess equalizing inside and outside temps.
 

sleepydoc

Member
Aug 2, 2020
423
406
Minneapolis
in every new car on the road, the defrost also engages the A/C to dehumidify the air. Your problem was that the cool air cooled the window down enough so that it caused condensation on the outside. The solution is to either turn off the defrost or turn up the temperature so it’s warming the window. I haven’t checked to see if you can manually disable the A/C in the Tesla but in most cars you can’t. Leaving it on ‘auto’ as others have suggested won’t make a bit of difference unless you adjust the temperature.
 
EVERY modern car since about the early 90s with AUTO hvac works best and most efficiently with the hvac set to AUTO! I am always baffled when people use manual settings with a car equipped with AUTO hvac.

I have had easily 25 cars since 1990, and I have used AUTO 70F in EVERY car in all weather from -25 to 122F and AUTO 70F has worked flawlessly...even with torrential humidity.
I've been trying auto on the Tesla. It sets the fan too high. It sets the fan too low. On a hot day, I want 66 or cooler. On a cold day, I want 72. And then I don't. I'm still futzing with the darned thing. Hence, I miss the good old physical manual controls.
 

CSGeekme

Member
Jul 29, 2021
46
30
Bay Area
I've been trying auto on the Tesla. It sets the fan too high. It sets the fan too low. On a hot day, I want 66 or cooler. On a cold day, I want 72. And then I don't. I'm still futzing with the darned thing. Hence, I miss the good old physical manual controls.
My previous car (kia Optima SX 2018) did the exact same thing. The fan would be set too high on a hot day and even when it got to the set temperature, cold air would still be coming into the car.
 

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top