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Temperature probe constantly showing too high reading


RedBarediver

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My temp reading on the dash is always about 30 degrees Celsius higher than actual Outside Air Temp. I have lived with it until now because I have had too many other things to sort out. Now that most of the big jobs are done I am starting to get around to doing all the fiddly little bits (and this is one that has been annoying me no end).

My question is; is this the only bit I need? Or, is there just a setting or something that I have to adjust with a OBD reader or something? My gut feeling is that the sensor is bad (for whatever reason) and I can get it sorted by just replacing the sensor. Does anyone have any experience with this repair? image.thumb.png.ec3df643d0a8d40383c2cbaf46b5de07.png

Edited by RedBarediver
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Did you check its properly seated?  If it has popped out, it might be sitting next to the radiator which will warm it up. Had the same happen on mine once. 

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19 minutes ago, Gutley said:

Did you check its properly seated?  If it has popped out, it might be sitting next to the radiator which will warm it up. Had the same happen on mine once. 

I was hoping that would fix it. I had the bumper off last week to do the condensers and checked the sensor then. It's properly seated and pokes out into the airflow. Still reads way too high though. Friday it was reading 55 degrees... I know it was hot but I'm sure it wasn't that hot! :)

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23 minutes ago, iborguk said:

Unless the car was parked in a fridge on Friday it wasn't 12C either ❄️🤭

I live in NI which has a similar climate to Scotchland so basically I live in a freezer 360 days of the year. 

-1 Celsius is approximately 30 deg Fahrenheit so always worth a shout but obviously a bit out there hence the :whistle: then add the fact I have no idea where Red is from, could be Finland  ;)

I don't know if the sensor is a thermistor, thermocouple, RTD or otherwise but all of which I have checked/offset for calibration BUT never for a 30 deg deviation  :laugh:

I have seen spurious readings when the wrong transducer is fitted i.e. type K thermocouple when it should be type J.

However corrosion/contamination  of the terminals/wires/connections can have a detrimental effect on the reading particularly if uncompensated and/or there has been a gas discharge nearby such as a leaking AC system?  ;)

Just my tuppence worth, I always encourage ideas from my engineers as even the daft suggestions can lead you up then down the correct garden path  :)

 

 

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5 hours ago, EXY said:

Set for Fahrenheit instead of Celsius  :whistle:

Good shout but no. It's degrees Celsius (I'm pretty sure) because the car has always been based in the UK. As a matter of interest, how does one switch between SI and Imperial units? I presume you need the correct OBD reader?

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18 hours ago, RedBarediver said:

Good shout but no. It's degrees Celsius (I'm pretty sure) because the car has always been based in the UK. As a matter of interest, how does one switch between SI and Imperial units? I presume you need the correct OBD reader?

IIRC it's in the binnacle menu, can't check mate as my 986 drove off over the horizon 3 years ago, sorry.

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Just checked again and it definitely is in Celsius. At the moment it reads 49.5 degrees Celsius and my iPhone says it's 19 degrees Celsius.

I am leaning towards just getting a new sensor and trying it out. I know it doesn't make a difference to the car's performance and is just there for information, but it bugs me when things like this don't work right. That's why I changed the screen in my heater / air conditioning unit as well.

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Worth doing - not sure the Boxster system is that sophisticated but on my daily shed Giulietta the climate wouldn't work properly when the outside temperature sensor did the same thing as yours.

Apparently it takes readings form 4 different sensors; the outside one being one of them 🤷‍♂️

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1 hour ago, Baldrick said:

Worth doing - not sure the Boxster system is that sophisticated but on my daily shed Giulietta the climate wouldn't work properly when the outside temperature sensor did the same thing as yours.

Apparently it takes readings form 4 different sensors; the outside one being one of them 🤷‍♂️

Yes, the 147 has the same. If the temp OAT sensor is incorrect it affects everything. Even the aircon apparently.

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Fixed. The new temp sensor sorted the issue. As soon as I installed it and turned the ignition on the temp started dropping from 49 degrees. It now reads 19.5 degrees and I'm sure that's correct. It has never shown such a low reading in my ownership.

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I had a similar problem on the Alfa Spider... i would have ignored it but for the fact tha tthe climate control was massively effected by what it thought the outside temp was! Fortunately it fixed itself in the following days before I had a chance to look at it.

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41 minutes ago, RedBarediver said:

As soon as I installed it and turned the ignition on the temp started dropping from 49 degrees. It now reads 19.5 degrees and I'm sure that's correct.

There you are folks. If you get cr*p summer weather this year in the UK, it's RBD's fault.

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