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For some weeks now my mother-in-law's Peugeot 207 (2009 model I think) shows a wrong outside temperature. While the actual outdoor temperature has been somewhere around freezing (0°C) the temperature display showed something like -7°C to -12°C.

It is not static but floats by some degrees up and down over the time the car is in use. First I thought it's just off by some 10°C or so, but it seems to be more complicated: Even if the car was parked in an underground parking for some hours where the temperature is surely around 10°C or warmer, the sensor then displays some -7°C or so. So to me it looks like it's some combined offset and proportionality issue.

Is there something I can try out myself to narrow things down or something that I can try to fix myself (connectors that could have gone loose or stuff like that)? If yes, where would I have to search? Or is this likely to be a software issue that needs a mechanic and special equipment?

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    Are you sure it's not set to show fahrenheit?
    – Pᴀᴜʟsᴛᴇʀ2 ♦
    Mar 2, 2015 at 18:58
  • @Paulster2 Definitely. Since -10°F is -23°C it would be even further off if this was the case.
    – Benedikt Bauer
    Mar 3, 2015 at 11:19
  • We have same problem It's showing the outside temp to be -3 on a 7 deg day !! I wonder if an air filter is blocked Going for a service anyway soon and will post a prediction
    – user10247
    Apr 24, 2015 at 16:12

3 Answers 3

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By looking at some French forums it seems the outside temperature sensor is located on the bottom of the right (passenger side) mirror, and is a standard NTC thermistor.

The signal is analog all the way up to some computer located inside the car, and the freaky values mean either the thermistor itself is dead or its cables are damaged. It can't be a computer issue otherwise the display would just show "--.- °C" or most likely not work at all and show an error message.

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i just had this dumb problems fix for good, for months even after i change the sensor at the mirror the problems of erractic temperture keeps coming back. today my mech took the bunch of socket out between door and the car body spray some contact cleaner and blow off any access with the pressure blower for abt 15 sec ......wah lah all back to normal , this require some additional hands as the door is quite heavy.

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  • It would be great if this would fix the problem. Could you take a picture of where to look at? From your description it's a bit hard to imagine it. Also does it require removing the door or parts of it (your answer sounds a bit like that)?
    – Benedikt Bauer
    Apr 29, 2015 at 16:03
  • it the bunch of connector at the body , i did not got a chance to snap a photo since i was holding the door while my mechanic blow off the vapour inside it. it not those socket at the door
    – user12131
    Sep 9, 2015 at 3:52
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In general, for all the temperature sensors (just a simple thermistors, i.e. resistors changing value according with the temperature):

  1. If indication is: - Large Value, e.g. -40, the sensor is not connected and the circuit is open.
  2. If indication is: + Large Value, .e.g. +40, there is short circuit.

Note: even when you connect the sensor and correct the circuit, in some automobiles need to be reset, by connecting/ disconnecting the circuit several times.

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