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Outside temperature accuracy

Big Dog

Active Member
Mar 7, 2016
1,639
1,631
Irvine, CA
thanks for posting this. I did a reading today and the display was 5 degrees higher than the actual outside temp (in the shade). But, then I moved the thermo to the bright sun, and it jumped 4 degrees, which was only one degree off of the display reading. Thus, its almost as if the display is showing the temp in the sun as if the thermo is heated by solar radiation. Of course, that is incorrect and why the correct way to read the temp is in the shade.

Anyone know where the thermometer is located on the M3? Attached to an exterior fender? Yeah, I get that this is a small nit, but still, my 18-year old Saab was excellent in this regard. Never off by more than one degree.
 

Scrith

Member
Jan 18, 2015
182
206
Redwood City, CA
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.
 
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irishndude4

Member
Feb 16, 2018
62
42
Pearland, TX
Yes I have noticed that on the display screen since I took delivery a couple weeks ago. Today it said 105 degrees after being parked outside for a couple hours. It was probably around the low 90s actually. Wish it was more accurate.
 

alseTrick

Active Member
May 17, 2016
1,646
892
Florida, USA
My cars have always over estimated temperature by at least 3 degrees.

Granted, they all are/were relatively old and i didn't own any of them new, do i don't know if the temperature discrepancy increased with age. And none were a Tesla.
 
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Whacker

Member
Jul 12, 2018
7
6
Virginia
I've consistently noticed the same 4 degree discrepancy. My old 5 series was always spot-on once it was in motion. Hopefully the battery thermometers are more accurate...
 
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eCharcoal

Member
Aug 31, 2017
288
297
Chicagoland
I’ve noticed in sunny days, the discrepancy could be more than 10 degrees. We had several days when temperature was around 87 degrees, the screen shows 100. Not sure this is fixable with a software update.
 

chinnam3

Member
Apr 26, 2018
328
231
Bellevue
Same thing here, it is always higher by 7-8 degrees, but when it was in sun it unusually high. My other 3 cars always showed correct temp (BMW, Honda, and Toyota),
 
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Saghost

Well-Known Member
Oct 9, 2013
8,217
7,010
Delaware
I’ve noticed in sunny days, the discrepancy could be more than 10 degrees. We had several days when temperature was around 87 degrees, the screen shows 100. Not sure this is fixable with a software update.

After parking on a sunny day, this likely isn't an error. The sun heats the parking lot, and the car is slowly baked from the outside in - while greenhouse effects heat the interior.

If it comes back down during driving, you're seeing real effects of the environment. That doesn't mean the sensor can't also be miscalibrated, though.
 

Shygar

Member
Aug 7, 2017
926
518
Pleasant Hill, CA
I would agree, but it should handle sitting in the sun. Other brand cars don't do this to the extent that I've seen it on the Model 3. Hopefully it can be a software fix but maybe not.
 

mytez

Member
Jul 6, 2018
6
1
Foothill Ranch, CA
Just to add more support....my 3 shows +10 in general. I thought this might be due in some way to my clear bra placement suffocating the sensor but if others are reporting misreadings then it saves me a phone call to the Tesla shop.
 

blackeducator

Member
Feb 22, 2018
66
50
coral springs, fl
The readings are an average around the car. AND, it is taking in the road/street level temp (which is obviously hotter than anywhere else!). So... if the street temp is 120° and the air temp is 90°, it'll give you an average reading around the car at around 105°. Also, if you are stuck in heavy traffic, the heat generated from other cars close to you will also raise the temp.

So... just look at it as an average instead of an accurate reading.
 
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chinnam3

Member
Apr 26, 2018
328
231
Bellevue
The readings are an average around the car. AND, it is taking in the road/street level temp (which is obviously hotter than anywhere else!). So... if the street temp is 120° and the air temp is 90°, it'll give you an average reading around the car at around 105°. Also, if you are stuck in heavy traffic, the heat generated from other cars close to you will also raise the temp.

So... just look at it as an average instead of an accurate reading.

Yeah, that is incorrect. It is supposed to show actual outside air temp, not the ground, not the temp of sun and that is what users expect like any other car out there. For that reason placement of sensor is very important, it should not be exposed to sun directly, neither supposed to expose to any parts that might cause incorrect readings. For example Prius temp sensor is mounted at the bottom grill behind bumper, so it is not impacted by sun light, rain etc, It only measures air temp. Not sure where Tesla mounted to cause so much deviation.
 
Last edited:

AlexanderAF

Member
Jul 7, 2018
94
236
Montgomery, Alabama
If you're looking for an accurate reading of the temperature outside, pay no attention to your car's thermometer.

On a warm summer day, it usually displays a temperature significantly higher than the actual temperature, and there are several reasons why. For starters, your car does not actually have a built-in thermometer, but a thermistor.

Most commonly, the temperature is measured with a mercury thermometer. The liquid mercury inside the thermometer expands and rises to a certain value when heat is added, and contracts and falls to a lower value when heat is removed.

A thermistor, on the other hand, measures the change in electrical current as a result of heat added or removed. The problem is not with your car's thermistor itself; in fact, thermistors are typically accurate, not to mention small and cheap to make.

The real problem is where the thermistor is located on your car. Most automakers place the thermistor on the front of the car behind the grille. This location exposes the instrument's readings to re-radiated heat from the road surface.

If you've ever walked barefoot on the beach or on a blacktop on a sunny day, you likely felt the re-radiated heat directly as your feet burned on the hot surface.

Car thermistors provide a better representation of nighttime temperatures, when the heating from the sun is lost. They are also more accurate on a cloudy day for the same reason, as well as when traveling at higher speeds and not sitting in standstill traffic.
 

Saghost

Well-Known Member
Oct 9, 2013
8,217
7,010
Delaware
If you're looking for an accurate reading of the temperature outside, pay no attention to your car's thermometer.

On a warm summer day, it usually displays a temperature significantly higher than the actual temperature, and there are several reasons why. For starters, your car does not actually have a built-in thermometer, but a thermistor.

Most commonly, the temperature is measured with a mercury thermometer. The liquid mercury inside the thermometer expands and rises to a certain value when heat is added, and contracts and falls to a lower value when heat is removed.

A thermistor, on the other hand, measures the change in electrical current as a result of heat added or removed. The problem is not with your car's thermistor itself; in fact, thermistors are typically accurate, not to mention small and cheap to make.

The real problem is where the thermistor is located on your car. Most automakers place the thermistor on the front of the car behind the grille. This location exposes the instrument's readings to re-radiated heat from the road surface.

If you've ever walked barefoot on the beach or on a blacktop on a sunny day, you likely felt the re-radiated heat directly as your feet burned on the hot surface.

Car thermistors provide a better representation of nighttime temperatures, when the heating from the sun is lost. They are also more accurate on a cloudy day for the same reason, as well as when traveling at higher speeds and not sitting in standstill traffic.

The heat burning your feet isn't being radiated - the asphalt absorbed the sunlight and is really that hot and is burning your feet through conductive heat transfer.

Similarly, I'd argue that the point you're making is basically the same as mine above - the car is in fact experiencing a higher local temperature than the general in the shade temperature reported on the news.

Solar heating of the roads combined with extra heat dumped by all the other cars on the road produce air above the roads that's noticeably warmer than the surroundings. On several occasions I've driven in an environment where there's substantial fog everywhere except along the heavily traveled interstate itself.
 
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