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Outside temperature accuracy

ZOMGVTEK

Member
May 19, 2015
559
442
'Merica
I don't suspect the car is reading the temperature wrong. It's more likely reading the temperature within 1-2 degrees of wherever the sensor is placed. This can be very different from the air temperature at times. Cars typically have some basic logic to minimize the error, but they all do this differently and its always an estimation. Some ICE cars hold the last reading from shutdown until the coolant temp drops below a certain value, since they know the hot engine is going to screw with the reading until it all cools down. Often the response is slowed so you don't get wild spikes, but you also don't get a true reading until some time has passed.

If you put a thermometer outside in the sun, it will read higher than the air temperature. This is not an invalid reading, its just telling you the temperature of the thermometer itself. There's really nowhere on a car you can put a sensor to get perfect air temperature readings, its a ballpark unless you're driving for a bit at decent speeds. If the car is parked, has been parked recently, has surrounding heat sources, or is moving slowly, it will be wrong. I don't see what Tesla can do about this other than just 'adjust' the reading. And then when its not in sunlight it will be reading low. They probably could get some advanced adjustments based on assumptions and other sensor data. But this is just a guess and it will still be wrong. I'm guessing they're just displaying the buffered sensor reading. Most cars are not very accurate. I'd guess Tesla has a very crude filter on the readings that hasn't been optimized. It's very likely they're well aware of this.
 
Last edited:

travis1906

Member
Feb 12, 2019
91
65
Haymarket, VA
Concur with the sentiments on the thread. Always much higher than actual temp outside. Not unusual for it to read 100 or higher and actual temp is not like 90 to 95. None of my other cars ever had this issue. Temp reading was essentially the same as the actual temp outside confirmed with multiple sources (phone app, temp readings on digital signs at banks, etc)
 

RScottyL

Member
Dec 19, 2016
269
163
Arlington, Texas
Yes, the Model 3 temp generally seems a bit high. My X holds the record though...once I came back to the car after it had been parked outside for a couple of hours and it said it was something like 135 degrees. It was around 90 outside.

I have seen this on many different cars when it has been sitting!

Once you get in and start driving, it will normal out!
 

richtrav

Member
Apr 20, 2019
139
124
South Texas
While not 7-10 degrees off, mine usually runs about 3-5 degrees too warm. As an informal test I have called a friend who is driving the same road right behind or in front of me and the reading on their car is at least 2 degrees cooler. It seems to be off more when the sun is out.
 

lolder

Member
Jun 11, 2016
949
852
SW Florida
This year has been warmer in SW Florida than any of the last 40 ! Usual temps are 92-95 and this year they are 95-98. I have two outside thermometers on my home on either side and note the lowest one. When I arrive home the M3 temperature agrees with them. I have seen 102 out on local highways that I have never seen before. This year is warmer all over the US and when the sun is shining on highways and there is little breeze, I believe the M3 readings are correct.
 

VanillaAir_UK

Well-Known Member
Jun 17, 2019
8,754
6,322
Surrey, UK
Never had a car that had a remotely accurate temperature sensor when left stationary in hot weather, in or out of the sun. You only need to start moving and it all changes.

They appear much more accurate at colder temperatures, especially close to freezing, when knowing the outside temperature is much more important to me.
 

Big Dog

Active Member
Mar 7, 2016
1,666
1,805
Irvine, CA
I don't suspect the car is reading the temperature wrong. It's more likely reading the temperature within 1-2 degrees of wherever the sensor is placed. This can be very different from the air temperature at times. Cars typically have some basic logic to minimize the error, but they all do this differently and its always an estimation. Some ICE cars hold the last reading from shutdown until the coolant temp drops below a certain value, since they know the hot engine is going to screw with the reading until it all cools down. Often the response is slowed so you don't get wild spikes, but you also don't get a true reading until some time has passed.

If you put a thermometer outside in the sun, it will read higher than the air temperature. This is not an invalid reading, its just telling you the temperature of the thermometer itself. There's really nowhere on a car you can put a sensor to get perfect air temperature readings, its a ballpark unless you're driving for a bit at decent speeds. If the car is parked, has been parked recently, has surrounding heat sources, or is moving slowly, it will be wrong. I don't see what Tesla can do about this other than just 'adjust' the reading. And then when its not in sunlight it will be reading low. They probably could get some advanced adjustments based on assumptions and other sensor data. But this is just a guess and it will still be wrong. I'm guessing they're just displaying the buffered sensor reading. Most cars are not very accurate. I'd guess Tesla has a very crude filter on the readings that hasn't been optimized. It's very likely they're well aware of this.

As a former STEM major, I get all that, and that is why in my earlier post, I only referenced deltas in the shade/cloudy day, so direct solar warming would not be a factor. My last two cars were generally within a couple of degrees of the surrounding temp; since both cars were 20+ years old, this is not exactly new technology stuff.

Obviously, not a big deal, but I only raised the question to others to help me understand if it was only my sensor that was off and needed to be replaced by the SC or, if that was just the way it is with other Teslas due to design/sensor placement. The latter appears to be the case.
 

LakeWorthB

Member
Jun 3, 2019
101
73
Lake Worth, FL
Officially the temperature stated by the weather service is with a thermometer in shade at least 6ft above grass. Any sun or heated car/asphalt will affect temp readings, so it is more surprising that it ever matches.
 

GolanB

Member
Supporting Member
Sep 22, 2018
620
734
NYC
From what I understand, the temperature sensor is located near the passenger side wheel well behind the front bumper. Someone had posted this video earlier of a front pumper disassembly and claimed it could be found here.

 

jebinc

MSM Model S PLAID, cream/FSD; MYP, white on white
Supporting Member
Jun 19, 2019
7,598
10,633
Seattle area
From what I understand, the temperature sensor is located near the passenger side wheel well behind the front bumper. Someone had posted this video earlier of a front pumper disassembly and claimed it could be found here.


If true, would the sensor pick up heat coming off the tire - especially if driving was "spirited"?!
 

GolanB

Member
Supporting Member
Sep 22, 2018
620
734
NYC
Yesterday during the heat-wave I saw one of the highest recorded temperatures on my Tesla (104F Outside, 133F Inside).

Screen Shot 2019-07-22 at 12.50.36 PM.png


I enabled cabin-overheat protection and its now keeping the cabin around 100 degrees. I'm already using sun screens for the top and rear windows, and will probably pick one up for the front windshield this week. They make a huge difference. I'm mostly concerned about electronic component and surface damage. I have heard of cases of warping and bubling of the dash surface.

Screen Shot 2019-07-22 at 12.54.45 PM.png
 

Mikeydeek

Member
May 8, 2018
144
49
Ottawa
As the temps are getting cooler now, I notice mine is showing around 4-5 degrees C warmer. This morning was 3 degrees on accuweather/weather network/radio and around 7-8 C on the car display.

However when I look at my trip reports on Tezlab, it shows the temperature the same as accuweather etc. Not sure where Tezlab is getting its temps from, but I assume from the car database somewhere? ...
 

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