Ambient air temperature sensor

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Your Car's Year / Make / Model: 13 Fiat Abarth

Ambient air temperature sensor

Post by Romanoaf » Fri Jan 31, 2020 10:09 pm

If your temperature isn’t displaying correctly the cause is likely a bad thermistor located in your right mirror housing.

FCA won’t sell you the sensor on its own, so you have a few options.
Buy a mirror assembly for around $100
Buy a used mirror assembly from a scrap yard, hopefully for under $50
Buy a sensor kit from the OEM in Italy - for 28euro
Replace the thermistor for around $0.25 (10k ohm)

You can test the sensor by reading resistance across the sensor, should read 10kohms @25 degrees Celsius +\- 3%

I chose to replace the thermistor.
First you’ll have to remove the mirror, by folding in the mirror removing the lower plastic cover, disconnecting the harness and removing the 2- 5mm socket head screws

Next you’ll need to remove the mirror glass and plastic back cap, recommend warming up the plastic so you don’t break any clips.

You should then see the sensor:
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At this point you can decide whether or not to cut and solder the new thermistor or re-socket the connector.
I cut and soldered.
The sensor rotates counter clockwise to remove.
I dug the old thermistor out of the resin on the sensor, and re-potted the new thermistor with 5 minute epoxy
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Install in reverse, there is no polarity on the sensor or the heated mirror wires, so it doesn’t matter which way it’s soldered/ plugged back in.
13’ Abarth

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Your Car's Year / Make / Model: 2013 Fiat 500 Sport

Re: Ambient air temperature sensor

Post by sportfan » Sat Feb 01, 2020 11:45 am

Good info ,thanks for sharing.

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Re: Ambient air temperature sensor

Post by texanbrit » Sun Feb 02, 2020 1:28 pm

This is brilliant! Many thanks for sharing!
2013 Abarth 500c (NGen Turbo'd) - Isabella
2012 500 Pop (stockish fauxbarth) - Popabella
2014 500L (just starting) - The Hulk
1971 850 Sport Spider (what was I thinking) - No name yet

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Your Car's Year / Make / Model: 2015 Fiat 500 Abarth
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Re: Ambient air temperature sensor

Post by MadFiat » Thu Feb 20, 2020 9:01 pm

Wow I was just thinking about this since my 500 Turbo's sensor reads about 10 degrees low.
2015 Rosso Abarth 5MT - MAD FIAT - EC Phase 2 + Supporting Mods
2015 Granito Lucente 500T 6AT - Projecto Estupido
2017 Fiat 124 Spider 6MT - Another one???

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Your Car's Year / Make / Model: 2013 500t

Re: Ambient air temperature sensor

Post by Chef_B » Sun Feb 21, 2021 12:36 pm

This is awesome, thank you for sharing!

Some important info that I learned: In the absence of input the computa assumes that its <freezing and runs very rich. If this is sensor is not reading accurately or you disconnect your passenger side mirror instead of leaving it dangling by the wires bc someone hit you and knocked it off your car, you should aim to address this as a priority for the sake of engine longevity. :-)

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Your Car's Year / Make / Model: 2015 fiat 500 pop

Re: Ambient temperature sensor solution

Post by Dsouza » Sat May 15, 2021 2:24 pm

The sensor can be bought on eBay instead of replacing the entire passenger side mirror
EC1EDE30-8C83-46BF-84F9-D8557090F3FC.png (382.08 KiB) Viewed 5041 times

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Joined: Fri Aug 06, 2021 12:00 pm
Your Car's Year / Make / Model: 2014 Fiat 500L Lounge

Re: Ambient air temperature sensor

Post by dapascale » Fri Aug 06, 2021 12:06 pm

Hi all! Bringing this post back from the dead!

My wife and I recently purchased a 2014 Fiat 500L Lounge and have already started experiencing this problem. We've had a hot summer, and those days when the reading is off and our car tells us there are 'Possibly Icy Roads' means we have been dying without AC.

We can't afford the $700+ quoted to us by the only Fiat service center nearby. Would anybody who has fixed the sensor on their own be willing to give me a tutorial of sorts? One written for a real simpleton? I'd also be open to a phone call if that is easier for some than typing everything out.


+ Daniel

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Your Car's Year / Make / Model: 2014 FIAT 500L

Re: Ambient air temperature sensor

Post by torresdd » Fri Oct 15, 2021 9:49 am

Hi dapascale

Did you ever get a response to your question? I too have a 2014 500L where the outside temperature varies widely and doesn't show the correct temperature. I have ordered the replacement part from here, but it says deliver date is anywhere from 7/Nov to 3/Dec. I will let you know what I do when I replace it.

Got the part in yesterday, 27/October/2021. It came from the Russian Federation. Waiting to isntall.

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