Loopy external temperature guage

[PeterE]

My external temperature guage seems to be obtaining its data remotely from the Tropics. After standing overnight it reads accurately agreeing more-or-less with the readings on our external guage in the house and those in the Mustang and Focus.

Thereafter on a journey, it just climbs slowly into the mid 20s and stays there even if its only 10C outside.

There are a number of posts on other BMW forums about this issue on other models so not unknown.

Does anybody else have this issue, if so a recommended solution apart from sensor change? It was OK when the car was delivered in February.

Thanks!

[ori]

Either faulty sensor or it’s dropped from its housing and is roughing something that warms up.

Car under warrantee right? Either book it in or get it sorted next service.

[dr_john]

I have never had this problem with my g29 or with the 3 e89’s I had.

Got to agree with ori’s comments

[ori]

I have never had this problem with my g29 or with the 3 e89’s I had.

Got to agree with ori’s comments

I didn’t have it on any of my zeds, but 20 years ago on a Porsche the sensor came out of its housing and would touch the rad. Caused all sorts of strange readings. Sometimes it would just hang in the sun and warm up that way.

[Nanu]

No problems with mine which seems accurate

[F1SpaceMonkey]

oddly i noticed mine state 23.5 degrees on drives this weekend when iPhone weather app stated 17. it was warm but not sure it was what the car was stating.

[PeterE]

Thanks everyone for the feedback/advice, I'll get this looked at when next in for a warranty service.

If I can work out where the sensor is I'll have a look at it, I think on the E89 it is under the front n/s wheel arch but not sure on the G29.

Of course, I don't need a temp guage to tell me when I can lower the roof...

[PeterE]

Update on this old thread - external temperature gauge issue investigated by Dealer as part of oil change service this week and confirmed as faulty, replaced under warranty.

My battery was low at about 50% too so I need to use the car more and hook up my battery conditioner regularly from now on.

[BobbyJ]

Ah, at last I have found others with the same issue.
The thermometer on my M40i also has an ‘optimistic’ approach to life. At initial start up and when pottering around town it reads accurately, but once up to motorway speed the reading begins to rise and ends up being about 6 degrees warmer than reality.
The car has been in to the dealer on several occasions, and the sensor has been changed (no effect), the software updated with a version direct from BMW Technical (no effect) and most recently the ‘combi unit’ (?) has also been changed (no effect).
So it seems that the sensor is working, but is sitting in airflow that is not truly reflective of the outside air. Could it be something to do with the active vents at the front of the car?
So far, nothing has that BMW has tried has had any effect whatsoever.
I thought I was all alone on this one!

[PeterE]

If it’s any help this is what my Dealer reported that they’d done

:“… NOTES - Investigated into outside temperature sensor showing incorrect reading. Read fault memory and found fault stored for power management. Carried out energy diagnosis, test plan advised 5 hour battery charge to get up to appropriate %. Charged battery and retested.
Disconnect temperature sensor, kombi control unit now reading at -40 degrees, default setting, reset and now showing -5.5%, suspected faulty sensor. Replaced sensor and reset kombi, retested following morning and now showing at correct temperatures...”

They did comment that the battery was only charged to 50% which could affect the accuracy but that doesn’t account for the misreading being evident last summer after a couple of 150 mile runs and the stop/start working which it doesn’t if the battery’s low.

I believe that the sensor is behind the LH front air intake and is a common part used across most BMWs including Minis. I guess it’s possible that this issue only affects the B58 i6 M40s as the engine is appreciably bigger than the B48 i4 but I don’t know.

Mine still reads slightly high compared to an old school mercury thermometer placed near it - when stationary of course - so will monitor closely in the coming months.

[BobbyJ]

Thanks for this.
Since the thermometers are reading ‘plausible’ temperatures rather than temperatures that could not possibly be, such as -40 degrees, the most obvious answer ( the Occam’s Razor approach) is that the thermometer is working properly, and it’s the airflow that is wrong, feeding the sensor air that has been warmed either by the engine or the radiator. It never, in my case, reads too low, always too warm.
Please do keep any updates coming.