Strange reading on temp gauge

[MisterB]

-37° ....? I'm assuming it's a fault, it's nowhere near that temp. When I drove a short distance it changed to about -20°, I stopped to put fuel in then started the engine and it went back to -37° as soon as I turned the ignition on again.
Can anyone shed any light on what might be happening and how I can resolve it please? Thanks

 

[SVMC15]

It'll probably be the thermocouple in the wing mirror. Mine went the opposite way! Not a hard job to replace it, just fiddly.

If you have an A class it could be somewhere else.

 

[Whippet93]

Had similar on a previous car, though not as bad. The temperature reading could vary by 15⁰ C driving a mile caused by a faulty external temperature sensor.

 

[Happy Jack]

Mine's been at +30 odd with slight variations for more than a year.
It'll be the thermistor in the wing mirror.
It doesn't bother me and causing no other faults so leaving it be.

 

[MisterB]

I've checked on t'tinterweb and the temp sensor also controls or sends signals to other parts of the vehicle, so should be replaced if it's faulty ?

 

[Lenny HB]

I've checked on t'tinterweb and the temp sensor also controls or sends signals to other parts of the vehicle, so should be replaced if it's faulty ?

Yes, it can affect DPF regeneration.

 

[Stoosal]

If it’s faulty I would change. If the vehicle does regens to clean dpf then it probably won’t do them unless temperature is within defined parameters. I doubt -37 would be one of them! Means that dpf will start to clog.

 

[MisterB]

I'll get one ordered tonight and fit on Sunday if it comes tomorrow..

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[Happy Jack]

Yes, it can affect DPF regeneration.

Oops, maybe I should change mine.
It's been at 30+ for more than a year now.

 

[pappajohn]

The one on my mobility scooter shows -37°
Last time used it showed a normal winter temperature of 2° or 3°
Cant do anything about it as its part of the dash display PCB.

 

[gus-lopez]

I've checked on t'tinterweb and the temp sensor also controls or sends signals to other parts of the vehicle, so should be replaced if it's faulty ?

Yes it does

Yes, it can affect DPF regeneration.

This^^^^^^^^^^^^

 

[Happy Jack]

Ordered one from hebay, arrived Friday.
Fitted it today, now reading correctly.

 

[the1andonly]

Temp sensor affecting regen. Oh no it doesn't. If its a Fiat that is (pre latest engine). Oh yes it does. Only with P&C engines with adblu. I dont know about latest 24 motors. iVe written about this pantomime before if you want the full answer.

 

[Happy Jack]

Temp sensor affecting regen. Oh no it doesn't. If its a Fiat that is (pre latest engine). Oh yes it does. Only with P&C engines with adblu. I dont know about latest 24 motors. iVe written about this pantomime before if you want the full answer.

Thanks, I was wondering why my Ducato had seemed to be OK for more than a year now with an ambient temperature reading of more than 40C.
Mine is pre adblue.
Fitting the new sensor was nice and easy.

 

[MisterB]

Temp sensor affecting regen. Oh no it doesn't. If its a Fiat that is (pre latest engine). Oh yes it does. Only with P&C engines with adblu. I dont know about latest 24 motors. iVe written about this pantomime before if you want the full answer.

Mine doesn't have adblu though? But I still intend changing it, strangely though it seemed to be working properly yesterday....

 

[Happy Jack]

Mine doesn't have adblu though? But I still intend changing it, strangely though it seemed to be working properly yesterday....

Wasn't going to bother, it had been 40C+ for well over a year now.
But from previous threads thought it could affect regen.
1 and only put me right, unfortunately after I'd changed it.
Anyway it was a simple job, and only a tenner from eBay.

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[the1andonly]

from an april post
just to clarify the sensor question
There are a number of ambient temperature sensors on the Ducato
1 IAT in the MAF sensor
2 with MAP sensor (not exactly ambient but is use to check MAF )
both controlled by engine ecu (high speed canbus)
3 temp sensor in mirror
controlled by body ecu.
with the Adblue models there are even more temperature sensors( on the fiat they are in a separate Adblu module.)
The temp sensor in mirror has a significance in regeneration of adblu models definitely Peugeot Citroen models. Was this then inherited by the adblu fiats just using the pre existing adblu methodology?
Does it have significance in regeneration of X250 or earlier ? No it was an optional extra on the X250 many with and without but have the DPF.
I suspect the IAT is used for the regen function, why? Because these are all important critical to the engine and are controlled by the engine ecu on the high speed can bus. The mirror sensor is controlled by the Body ECU on the lo speed canbus and is used by electronic climate control and the comformatic.
The information in the X290 Converters Manual implies that (at least for non Ad-Blu models, which it pre-dates) the external temperature sensor is a requirement only when the vehicle is fitted with Automatic Climate Control and/or the Comfortmatic gearbox. Some vehicles are provided as Chassis Cowls, without any mirrors (or doors ) and thus the converter must add a sensor elsewhere. Hence the questions wheres my Hymer A class temp sensor.
Thus the mirror sensor does have a significance but not to the extent of the Doom and Gloom merchants i've read elsewhere (i repeat elsewhere) .

On reading more Fiat doccumentation the DPF temp sensor is the one involved in DPF regen

 

[MisterB]

from an april post
just to clarify the sensor question
There are a number of ambient temperature sensors on the Ducato
1 IAT in the MAF sensor
2 with MAP sensor (not exactly ambient but is use to check MAF )
both controlled by engine ecu (high speed canbus)
3 temp sensor in mirror
controlled by body ecu.
with the Adblue models there are even more temperature sensors( on the fiat they are in a separate Adblu module.)
The temp sensor in mirror has a significance in regeneration of adblu models definitely Peugeot Citroen models. Was this then inherited by the adblu fiats just using the pre existing adblu methodology?
Does it have significance in regeneration of X250 or earlier ? No it was an optional extra on the X250 many with and without but have the DPF.
I suspect the IAT is used for the regen function, why? Because these are all important critical to the engine and are controlled by the engine ecu on the high speed can bus. The mirror sensor is controlled by the Body ECU on the lo speed canbus and is used by electronic climate control and the comformatic.
The information in the X290 Converters Manual implies that (at least for non Ad-Blu models, which it pre-dates) the external temperature sensor is a requirement only when the vehicle is fitted with Automatic Climate Control and/or the Comfortmatic gearbox. Some vehicles are provided as Chassis Cowls, without any mirrors (or doors ) and thus the converter must add a sensor elsewhere. Hence the questions wheres my Hymer A class temp sensor.
Thus the mirror sensor does have a significance but not to the extent of the Doom and Gloom merchants i've read elsewhere (i repeat elsewhere) .

On reading more Fiat doccumentation the DPF temp sensor is the one involved in DPF regen

I wonder why vehicles with comformatic gearboxes must have it fitted? Is it something that contributes to it's smooth running?

 

[Graydo]

My Fiat sensor is wonky too, but it doesnt affect regen.
Non ad blu, non comfomatic 2019 model.

I was told only affects Citroens amd Peugots.

Graydo