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

[David29]

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.

I suspect so, as well, and I hope so, but the owner's manual does not say so.

 

[David29]

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?

According to the owner's manual, when you double-click the Defrost button, you get maximum fan speed and maximum heating, which implies that the temperature control setting will no longer apply. Which supports someone's earlier statement that a single click leaves the temperature setting as it was but directs air to the windscreen. By the way, that function times out and shuts off after a while.
If you want to direct air to the windshield and leave it like that, you can do so with the manual controls by clicking on the fan button and setting the air flow to include the windshield. This is useful in winter if you want to be able to preheat the car AND include the windshield. if you leave the airflow set to the windshield (with or without any other airflow settings), it will remain like that until you set it back. I do this when I expect snow or ice overnight, to facilitate clearing the windshield while preheating. If you leave it in AUTO and preheat with the phone app, you rely on the car to decide whether or not to run the defroster (sometimes it does, but it may shut off too soon).

 

[David29]

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

It probably tries, and I do see it run the defroster on cold days. But it does not necessarily run it very long, so it may or may not run it enough for melting snow or ice off the glass.
See my further note above -- you can set the airflow manually if you want more control over what the car will do when you preheat.

 

[Saghost]

According to the owner's manual, when you double-click the Defrost button, you get maximum fan speed and maximum heating, which implies that the temperature control setting will no longer apply. Which supports someone's earlier statement that a single click leaves the temperature setting as it was but directs air to the windscreen. By the way, that function times out and shuts off after a while.
If you want to direct air to the windshield and leave it like that, you can do so with the manual controls by clicking on the fan button and setting the air flow to include the windshield. This is useful in winter if you want to be able to preheat the car AND include the windshield. if you leave the airflow set to the windshield (with or without any other airflow settings), it will remain like that until you set it back. I do this when I expect snow or ice overnight, to facilitate clearing the windshield while preheating. If you leave it in AUTO and preheat with the phone app, you rely on the car to decide whether or not to run the defroster (sometimes it does, but it may shut off too soon).

The car remains consistent in its response to the temperature setting even in Red defrost - because when you hit Red, it overrides the previous temperature setting with HI, and keeps it there until you switch back out of Red defrost.

Turning the temperature down while in Red drops the car back into auto (out of defrost entirely) and back to your prior temperature. Hitting defrost again does the same thing.

 

[r1200gs4ok]

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

this is the best response

 

[ucmndd]

this is the best response

I’m glad I can stop worrying about this one, it’s been bugging me for two years. Thanks.

 

[MikeRadio]

I know this is an old thread, but this is something I’m always wondered about myself.

When I use the voice command, defrost front window opposed to default front window. What am I getting with each of these? There have been times where it defrost right away and other times where it seems to take some time.

Usually with ice cars sending air to the front windows temperature is whatever you have it set to the car. There is no blue and red. Obviously our cars are much more advanced.

I defogger I usually just use the voice command because it’s easiest. and also I didn’t notice on the assignment. Scroll wheel on the left you can only assign defrost.

 

[David29]

I know this is an old thread, but this is something I’m always wondered about myself.

When I use the voice command, defrost front window opposed to default front window. What am I getting with each of these? There have been times where it defrost right away and other times where it seems to take some time.

Usually with ice cars sending air to the front windows temperature is whatever you have it set to the car. There is no blue and red. Obviously our cars are much more advanced.

I defogger I usually just use the voice command because it’s easiest. and also I didn’t notice on the assignment. Scroll wheel on the left you can only assign defrost.

Not quite sure I am following your explanation. But in every car I have owned before I had a tesla, there was a "Defrost" button and also air controls that could direct air in various ways, usually including an option for "bilevel" flow that went to the windshield and the floor. The "Defrost" function always ran full heat, maximum temperature and maximum fan speed. Plus it ran the AC compressor (so long as the temperature was high enough to do so). The "bilevel" flow was, as you describe, at whatever level of heat you had set. The red Tesla defrost buttons apparently corresponds to other cars' "Defrost," with max air flow, max temp, and AC. The blue one is just a way to direct the air to the windshield at whatever the temp setting is. Makes sense to me, and always worked as expected, so far as I can recall. (I had a Model S 70D for 8 years, since new, but recently traded it in on something else.)