I own a 2004 Subaru Forester XS with 102,000 miles on it and required service and inspections just completed.

Now the Ambient Temperature Gauge keeps malfunctioning - often sticks at 77; after a few hours it shows the correct outside temperature. What could be wrong?

The mechanic cannot explain to me why the gauge starts to work after a few hours if I stop the car and go shopping. When I return, the gauge starts working again. He says it is not a loose connection but he has not checked any of this out yet.

By the way, the mechanic did disconnect and drain the AC system while he was working on the car -- I do not know why he did this although I think it was a mistake since I was not charged for this. The AC works fine now as it did before.this link shows where the sensor is that the mechanic pointed me to on the dashboard of the passenger side. enter image description here

  • I'd be concerned if a mechanic did work on my car without my knowing in advance what was to be done - especially related to the AC system, which requires special equipment to work on it safely.
    – PeteCon
    Commented Jul 11, 2016 at 16:33
  • Thank you for your comment. I agree. It was indeed a mistake on their part and I should not have said "I think it was a mistake" since the service manager did say it was a mistake. But could this have anything at all to do with the gauge on my dashboard that only reads correctly part of the time? The mechanic there showed me a round sensor on the passenger side of the car on top of the dashboard and said that was where the readings were taking place.
    – Joan
    Commented Jul 12, 2016 at 12:56
  • @Pete -- Thank you for your input so far and for the diagram. Here is a diagram of where the aforementioned sensor sits in the dashboard.
    – Joan
    Commented Jul 12, 2016 at 14:20

1 Answer 1


Sounds like the temperature sensor is broken. A new one is $40-$55, and it's a 30 minute job to replace if you've never done it before (it lives behind the grill in front of the radiator). Not uncommon for these to fail on Subarus and give weird readings.

Following Paulster2's comment, here's an image of what the sensor looks like;

Image from http://www.autozone.com/emission-control-and-exhaust/sensor-ambient-air-temperature/duralast-sensor-ambient-air-temperature/179833_0_0/

In this image (of a 2007 Forester), the sensor is in the yellow outlined location.

enter image description here

  • Can you include a pic of where it's at and what to look for? Might help others in the future as well as the OP. Commented Jul 11, 2016 at 20:42
  • How do I post a picture of the sensor on top of the dashboard on the passenger side? I have found the diagrams of the parts but I do not know how to post the picture.
    – Joan
    Commented Jul 12, 2016 at 14:27
  • Hi Joan - The sensor your mechanic pointed out is the Solar Sensor (part of the internal climate control system, but not the bit you're interested in) - see techinfo.subaru.com/proxy/71914/pdf/ownerManual/… (page 8). The outside temperature sensor - which is the one I believe has failed - is behind the front grill of the car.
    – PeteCon
    Commented Jul 12, 2016 at 16:10

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