What's the difference between the Hot and cold defrost options?

[PhilDavid]

I noticed that the front windshield defrost mode has two options. When you enable it initially, it is blue, and I assume it is blowing cold air. If you long press the front windshield defrost button it turns red, and I assume blows warm air.

I'm not sure which mode to use when. I'm a bit surprised the car does not figure out which mode to use by itself or does it based on which mode it turns on with?

 

[murphyS90D]

If the outside air has high humidity and you use cold air defrost it will cool the windshield and condensation will form on the outside of the glass. The wipers will have to be run manually to clear it off of the glass.

 

[SSedan]

I think the blue option is cabin temp not cold, red is full blast heating and uses much more energy.
An ICE has so much heat energy to waste they don't give you these options.

 

[Saghost]

The Blue option directs air to the windshield vents, but continues to maintain your set cabin temperature, warmer or cooler than outside as it may be.

Red overrides the temps, sets to "HI" and forces maximum heat onto the windshield.

 

[DCEV]

The Blue option directs air to the windshield vents, but continues to maintain your set cabin temperature, warmer or cooler than outside as it may be.

Red overrides the temps, sets to "HI" and forces maximum heat onto the windshield.

Thanks! I learned something new

So basically in general the best option is the Blue Defrost option... When is it advantageous to use the Red Defrost option?

 

[Dithermaster]

I thought it was a second press (within some time window) that made it read, not a long press? Maybe both work, but I've only used the first.

 

[ucmndd]

When is it advantageous to use the Red Defrost option?

Cold temps, when you want to defrost the window as soon as possible.

 

[Saghost]

Thanks! I learned something new

So basically in general the best option is the Blue Defrost option... When is it advantageous to use the Red Defrost option?

Blue is subtle, blends in to your usage with no inconvenience and no wasted power, but might take time to achieve the desired result.

Red has the raw power to defrost quickly when you need it, even if it overshoots your preferred cabin temps in the process.

So Red is mostly for when you're in a hurry and didn't precondition, or for when Blue can't keep up with the severe inclement weather.

 

[DCEV]

Blue is subtle, blends in to your usage with no inconvenience and no wasted power, but might take time to achieve the desired result.

Red has the raw power to defrost quickly when you need it, even if it overshoots your preferred cabin temps in the process.

So Red is mostly for when you're in a hurry and didn't precondition, or for when Blue can't keep up with the severe inclement weather.

Hmm... If that's the case I will always use the red defrost option, if I'm about to drive and use the blue defrost option if I'm parked. If I'm driving or about to drive, being able to see clearly is a matter of safety so I would want the windshield to be clear as quickly as possible with no regard to energy use.

 

[PhilDavid]

Anything else anyone want o add to the how the defrost modes should be used or is it generally use blue if not critical and red/hot air if you want the defrost to be quick?

 

[Hota]

In most cases you want to use the blue "defrost" - not because it saves energy but because in most cases (even in ICE) cars, you want to use the AC compressor while defrosting/defogging. Using AC removes the humidity from the air and dries off the inside of the windshield.

Blue = Defogger = Clearing fog on inside of windshield
Red = Defroster = Clearing frozen stuff on outside of windshield

 

[PhilDavid]

In most cases you want to use the blue "defrost" - not because it saves energy but because in most cases (even in ICE) cars, you want to use the AC compressor while defrosting/defogging. Using AC removes the humidity from the air and dries off the inside of the windshield.

Blue = Defogger = Clearing fog on inside of windshield
Red = Defroster = Clearing frozen stuff on outside of windshield

That's really helpful. Thanks!

 

[DCEV]

In most cases you want to use the blue "defrost" - not because it saves energy but because in most cases (even in ICE) cars, you want to use the AC compressor while defrosting/defogging. Using AC removes the humidity from the air and dries off the inside of the windshield.

Blue = Defogger = Clearing fog on inside of windshield
Red = Defroster = Clearing frozen stuff on outside of windshield

I've heard the best way to address fob build up is to use both. Basically heat towards the windshield PLUS run the AC at the same time to remove humidity. Some high end cars do this automatically. Do we know if Tesla software can heat the windshield plus run AC at the same time?

 

[murphyS90D]

I have run into a different situation. On a hot day, which requires air conditioning, but with very high outdoor humidity and the sun hidden by clouds condensation forms on the outside of the windshield because cold air is blowing on it. The wipers will remove it. Apparently if the eye level vents are not enabled they send the air to the windshield so enabling the eye level vents should prevent the outside condensation.

 

[Barry]

Do we know if Tesla software can heat the windshield plus run AC at the same time?

I believe AC is automatically turned on in defrost mode

 

[Saghost]

I've heard the best way to address fob build up is to use both. Basically heat towards the windshield PLUS run the AC at the same time to remove humidity. Some high end cars do this automatically. Do we know if Tesla software can heat the windshield plus run AC at the same time?

Pretty sure the car is running AC to dry the air that it's heating to blow on the windshield, but I'm not sure we have a way to know for certain. That's been more or less standard for defrost modes for a few decades now in nearly all cars.

 

[drklain]

For most cars the compressor is running for defrost mode whether it is on hot air or cold air. For those of us older folks who remember the old "slide levers" climate control systems...there were two levers. The first selected the mode - off, fan, air condition or defrost. The second selected temp -- from hot to cold. A little light would come on if AC was selected...it illuminated for both air condition and defrost modes. My kid's 2012 Ford Focus indicates the same thing (a/c light on for air condition or defrost mode selected). I suspect the Tesla does the same thing.

 

[Chaserr]

When is it advantageous to use the Red Defrost option?

When the glass is covered with ice. The app does this automatically when you precondition in frozen temperatures (you will see the defrost icon).

 

[DCEV]

When the glass is covered with ice. The app does this automatically when you precondition in frozen temperatures (you will see the defrost icon).

So it seems like the car picks the best default option automatically based on current conditions?

 

[Chaserr]

Maybe? There's no symbol for it in the app when it's warmer. I don't think it uses the defroster for preconditioning unless it's cold enough to freeze.