Condensation on windshield on the inside

[Red Matter]

In recent days, when the temperature has gone quite low (around 0 deg Celsius), there has been a build up of condensation on the inside of the windshield in front of the driver seat. Temperature inside the car has been 3-4 degrees Celsius, which is understandable given the low temperature outside. Turning on the windshield defroster takes care of the condensation but it takes about 10 mins to dry the water to an extent where it is clear to drive but still leaves water marks which are annoying.

We drive with the climate control always on and don't do anything different to what we would do in our other car. Thought it was a one off but it has happened a few times now. After decades of owning cars, this is a first for me. Has anyone else had this problem? Any words of wisdom on how to prevent it?

 

[Saimaannorppa]

There is no other way around it except to prevent moisture entering the cabin in the first place. Water builds up to the carpets each time you bring in snow or water.

You can buy chemical dehumidifier, but they work slow especially in cold climate. One should be present already before cold time starts. Rubber carpets enable you to dry the water before it is absorbed and ultimately condensating on cold surfaces.

 

[jdw]

You could try turning off auto recirculation so fresh air enters the cabin.

 

[tktktk]

Bought a brand new S on Friday and have the exact problem. I've never experienced this in other cars to the extent I am now. I did turn off auto circulation but it did not stop ice from forming. Disappointing to say the least. Driving and scraping ice off the window with a credit card is less than ideal.

 

[jdw]

More specifically, I turn AC off, recirculation to fresh air (for at least the first 10 minutes or so), turn on all three heating levels manually and leave the fan on auto with temperature set to 22C. No fog or ice down to -25C.

 

[mrElbe]

I leave the whole HVAC on Auto and set the interior temp to +20C. Absolutely no problem as described.

 

[Dax279]

I find that when I get some moisture on the inside of the car that running the A/C helps get rid of things pretty well. I also try to avoid re circulating the air a bit.

I also agree that when things get cold manually setting things works better than auto.

However, I’m thinking you have a bit more of a moisture issue by the sound of it OP. The condensation sounds like it is there before you even get into the car?

 

[Saimaannorppa]

More specifically, I turn AC off, recirculation to fresh air (for at least the first 10 minutes or so), turn on all three heating levels manually and leave the fan on auto with temperature set to 22C. No fog or ice down to -25C.

This works too, as the cold air is extremely dry. 99% RH air at -20C is something like 5% RH in room temperature.

Another trick is to vent out the moist heated air after trip, before it absorbs and cumulates on textures and surfaces.

These are addressing the symptoms though. Solution is to not bring in too much water in the first place.

 

[tktktk]

This works too, as the cold air is extremely dry. 99% RH air at -20C is something like 5% RH in room temperature.

Another trick is to vent out the moist heated air after trip, before it absorbs and cumulates on textures and surfaces.

These are addressing the symptoms though. Solution is to not bring in too much water in the first place.

Thanks all. Will try these suggestions.
Car is probably fine and sealed tighter than other vehicles I've owned. If all else fails, I will stop breathing.

 

[OlderThanDirt]

It is cold here -20 fahrenheit and defrost works very well. Are you actually turning on the defrost?? The first touch of the defrost circulates cabin air across the windshield. A second touch turns on heat to the defrost. We keep the HVAC on auto and mostly just circulate cabin air across windshield if needed. It's in the manual pg 102.

 

[PGeer]

Our temps are much milder here in Seattle area, but occasionally have the same problem with condensation when temps in high 30's. Auto usually has the AC off in these conditions, and I've found that manually turning it back on quickly clears the problem. Don't know if that works when a lot colder and the air already much drier.

 

[aesculus]

Revising an old thread. Recently I have been doing some driving in colder climates (45F to 15F) and have been experiencing some pretty rapid buildup of condensation on the windshield and side windows. This is mostly happening with temps are around 25 to 35F. I am on V9 50 but also experienced it on 48.

Playing with it today I discovered I could keep it clear if I turned on the blue front window defogger and also of course the red setting. Going into the climate controls when on Auto I noticed when the temp was below around 40F, the A/C was off and it looked like the default was recirculation. Above about 40F it seems that outside air is the default and A/C on.

Up until V9 I never noticed the car fogging up so much before.

It seems crazy that I either have to manually play with the window defogging control constantly, alter the A/C and/or recirculation settings.

Do others in colder climates with humidity have this issue too?

 

[SilverSp33d3r]

In recent days, when the temperature has gone quite low (around 0 deg Celsius), there has been a build up of condensation on the inside of the windshield in front of the driver seat. Temperature inside the car has been 3-4 degrees Celsius, which is understandable given the low temperature outside. Turning on the windshield defroster takes care of the condensation but it takes about 10 mins to dry the water to an extent where it is clear to drive but still leaves water marks which are annoying.

We drive with the climate control always on and don't do anything different to what we would do in our other car. Thought it was a one off but it has happened a few times now. After decades of owning cars, this is a first for me. Has anyone else had this problem? Any words of wisdom on how to prevent it?

What year is your vehicle? Have you had The desiccant replaced in the Air Conditioning system? Should be part of normal maintenance if you take the vehicle to tesla for service.

 

[Benjanos]

It's my first winter with the Model S, so not a lot of experience but yes it's fogging up a lot. I notice the ventilation tends to default back to re-circulation which makes things worse so I need to remember to go in change that before setting off. Wonder if the more recent SW versions force the car back to recirc whereas perhaps previous versions remembered the previous setting?

Also preheating on recirc is going to steam things up nicely before you even get to the car I guess?

 

[SilverSp33d3r]

Have you tried just letting the car select the right settings by leaving it on Auto? Are you tracking tons of water/snow into the vehicle?

 

[Jan Fiala]

This problem comes with the V9 software version. It handles the climate control settings differently rendering the auto settings pretty much useless when handling windows fogging. I've never ever had this problem prior V9.

 

[Saimaannorppa]

Exactly as Jan puts it. The idea of such change probably is to use even less energy, but where would the humidity go if you’re not letting dry air in nor using A/C to dry the air? Answer: it builds up on the coldest surface, which is the windshield and other glasses. If you’re running A/C, the coldest surface is the evaporator.

I’m using manual setting almost all the time since v9 came out (which are: using all vents, no recirculation, blower 5 or 6, A/C on or off depending on if there is fogging). Still, the best way to prevent fogging is to not Bring in any extra water.

 

[TSLA Pilot]

What year is your vehicle? Have you had The desiccant replaced in the Air Conditioning system? Should be part of normal maintenance if you take the vehicle to tesla for service.

This has nothing to do with OP's issue.

The desiccant in the AC system is apparently being used to remove moisture that is INTERNAL to the closed R-134a gasses in the HVAC system. This is standard practice, what is NOT however (to my knowledge) is opening up a sealed system to replace this on a regular basis.

Not one other brand requires this service--what gives Tesla?

 

[dark cloud]

Well here is what BMW says:

BMW Air Conditioning Recharge.
If you find that you are unable to achieve a comfortable temperature or de-fog your windscreen on a cold morning, your car may need an air conditioning recharge. A BMW Recharge Service is the perfect fix and includes full system checks for both pressure and leaks, as well as a complete drain and refilling of refrigerant and lubricants. And as to be expected, the BMW Air Conditioning Recharge Service comes with a level of expertise only available directly with BMW.

Air Conditioning Service | Servicing and Repairs | BMW UK

 

[dark cloud]

I’m using manual setting almost all the time since v9 came out (which are: using all vents, no recirculation, blower 5 or 6, A/C on or off depending on if there is fogging). Still, the best way to prevent fogging is to not Bring in any extra water.

For people in colder climates using manual settings who turn off the A/C, a reminder to ensure you engage it regularly to extend life of the system. I am not sure if Tesla has programmed the computer to make sure it cycles regularly or not, but not using the A/C system is what kills it.