Inaccurate temperature readings

[LiamPope]

Hi. Anyone noticing, or experienced before, inaccurate exterior temperature readings on the screen?

Mine will frequently read lower at the start of a drive. For example I went to it today, about 4 C outside, but it reads -7! Towards the end of the short trip it jumped up to -1. Has done this several times recently. Other times it seems accurate.

Wonder if it's update related, and others have it, or it could actually be a faulty sensor. Also wondering if this could be related to the car being in auto defogging mode much more than it should, which I know is covered in another thread.

Please don't tell me I missed the news about Elon switching to Vision where the cameras and AI look at what people are wearing out to determine the temperature!

 

[brkaus]

Which Model Tesla?

Edit - Oops. I see in your sig when I turn phone in landscape - 2022 model 3LR

 

[LiamPope]

Which Model Tesla?

Edit - Oops. I see in your sig when I turn phone in landscape - 2022 model 3LR

Yeah sorry, should probably put it in the text anyway. 2022 3LR indeed.

 

[brkaus]

Then I have no suggestions. I read the newer m3 uses the internet and has no temp sensor.

 

[billuk]

I experience this from time to time and have wondered.

It's never been frequent enough or problematic enough that I have taken it any further so far.
(M3LR / Dec 2020)

 

[init6]

Some folks on this thread (covering quite a few years) have had either the sensor/harness/or louvres replaced when they had the same issue.

Wrong outside temp reading

My outside temperature is stuck and remains on 68F no matter what the real temperature is. I don't know what causes this to be broken. I scheduled Tesla service to fix it. If there's a DIY fix, I'd like to know.

teslamotorsclub.com

Also mentions a thermal test which may be accessible from the service manual if you fancy a look. Might be worth a service request.

 

[The Lorax]

Then I have no suggestions. I read the newer m3 uses the internet and has no temp sensor.

I read the same thing. As it's now getting the temp info from the internet, in addition to choosing between C or F, you now can select either liberal or conservative weather sources, i.e. the "The Earth is going to end in twelve years" or "Climate Change is a hoax" websites. You can still select 'old fashioned' and just have the temp displayed in C or F, but that automatically puts the car in 'Chill' mode and prevents you from passive-aggressively overtaking VW drivers on the motorway.

 

[ACarneiro]

I read the newer m3 uses the internet and has no temp sensor.

Wait, what??
A thermistor was too expensive ("á la Rain Sensor and USS)?

Jesus, it gets crappier and crappier....

 

[LiamPope]

Wait, what??
A thermistor was too expensive ("á la Rain Sensor and USS)?

Jesus, it gets crappier and crappier....

I read that ages ago too, but not sure if it's actually implemented. But to be honest that would be much more accurate than what my sensor is doing at the moment.

 

[dcfas]

My temp reads the garage temperature until I’ve driven the car for about 13-15 minutes. Then it abruptly adjusts, like changes from 45 to 21 in a blink.

As a side note, I believe the speedometer is fast by one to two mph.

 

[MrBadger]

As a side note, I believe the speedometer is fast by one to two mph.

Our 2019 Model 3 is absolutely spot on with GPS (at any speed) and roadside radar speed signs (usually in 20 and 30 limits). Irrespective of summer/winter tyres.

Most accurate Speedo we have has on a car.

My other car is ~ +2/+3 at 70 and +0/+1 at 30. That’s on cross climates and can’t recall it being any different on manufacturers summers. Well within the -0%/+10% iirc allowed tolerance.

 

[MrT3]

Well within the -0%/+10% iirc allowed tolerance.

The allowed tolerance is different in the US and can read under so it is more common for them to be accurate. But even tyre wear will vary the displayed speed by 1 or 2 mph if speed is derived from the wheels (I.e. not gps).

Mine seems to read about 1 mph over at 40 mph but is certainly the most accurate car I’ve had. My wife’s Lexus is reading 44 at 40 mph.

 

[thax1]

The allowed tolerance is different in the US and can read under so it is more common for them to be accurate. But even tyre wear will vary the displayed speed by 1 or 2 mph if speed is derived from the wheels (I.e. not gps).

Mine seems to read about 1 mph over at 40 mph but is certainly the most accurate car I’ve had. My wife’s Lexus is reading 44 at 40 mph.

Agree.
We have a number of the light-up speed signs locally now, they typically show 29mph as I trundle past with cc set to 30 in the MY.

My previous Lexus was comedic in its speed under reporting, took a while to realise why I was being overtaken in 40mph areas for dawdling. Still it was rather addictive wafting around like that, and soooo quiet

 

[KennethS]

Car manufacturers seem to be very careful to ensure the speedometers don't under report. Obviously they want to avoid any culpability for a speeding violation. It may even be a regulatory requirement. That said, some of our previous cars had quite a large margin when overstating speed. Our Tesla are nearly spot on and overstate by a very small margin.

 

[MrT3]

Car manufacturers seem to be very careful to ensure the speedometers don't under report. Obviously they want to avoid any culpability for a speeding violation. It may even be a regulatory requirement. That said, some of our previous cars had quite a large margin when overstating speed. Our Tesla are nearly spot on and overstate by a very small margin.

Regulation I believe. Here are the stats for my old Lexus in the European repair manual - if it actually reads the correct speed it cluster should be replaced as faulty as by design it should read over:

But if you consult the US version of the manual it has different values which are lower. The clusters have different part codes per region because they are calibrated differently.

For vehicles with different wheel size options there is normally up to 2% speedo difference between them which the manufacturers don't recalibrate for - they just allow their large tolerance to accommodate the options.

I don't know if Tesla recalibrates when you select different wheels or not.

 

[LiamPope]

I'll raise a service request and see what happens.

 

[LiamPope]

Minor update. So I had a mobile visit. Pushed some firmware and did a regular update. Didn't fix it - e.g. the other day 5 degrees out, car reading -4. Next drive seemed accurate.

Going in next week, work order says

Active Grille Shutter (Remove & Replace)
Thermal System Test
Adjustment: Exterior Trim

Previous work order also had the last two items, but the mobile tech said nah it's not that.

 

[LiamPope]

Thought I should follow this up.

It went in for the work above - replace the ‘active grill shutters’ - and all is good now with temp readings and AC behaviour. I was scratching my head how a non faulty temp sensor (they insisted the sensor was fine) could ever read lower than ambient. To hot, sure, if it’s mounted in an area that can trap hot air, but too low???

I guess I just wasn’t thinking heat pumps! Heat pumps of course will generate sub ambient temps in the system. So I guess the ambient temp sensor must be situated somewhere where the failure of these ‘active grill shutters’ exposes it to sub ambient temp air. Shutters fixed (they confirmed they were indeed stuck) and it’s all working correctly.