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Ambient Temperature Sensor on the fritz. What to do? 850 1996

posted by  someone claiming to be Hugh on  Mon Feb 8 14:42 CST 2021 [RELATED]

Hello All,

I have a 1996 850 GLT Wagon, non-turbo with a 5 speed manual, with 355,000 miles on the odometer. Today, out of the blue, the ambient temperature sensor started giving a temperature reading approximately 20 degrees warmer than the actual outdoor temperature. This car has its original ambient temperature sensor.

The ambient sensor is located in the engine bay, just beneath the radiator. I called my local Volvo dealer, and confirmed the ambient temperature sensor is still available (Part # 1347010, Retail Price : $38.32). Before I go off and purchase a new ambient temperature sensor, could anything else be causing this inaccurate temperature reading? We did experience snow here in CT yesterday, but I only drove on plowed roads, plus I've driven this car through snow storms before without any impact on the ambient temperature sensor. I confess a reluctance to have to crawl on my back to replace this sensor, if it is indeed the cause of the problem. Of course it fails in the winter!

Thank you in advance to all who respond. Your collective knowledge is my greatest treasure!

Hugh








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    posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

    I was under the impression that the temperature sensor is also used by the car's computer.

    I checked my Haynes 850 manual, I could find no mention of the temperature sensor.

    Perhaps you can check with a dealer to find out if my impression is correct.



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      posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

      Yes, it is. The computer uses it to measure air density in relation with the MAF. But, the temp being off a 10-20 degrees doesn't change the air/fuel mix very much, so drivability is not effected.

      The 1998 cars had 2 sensors, one for the temp display and the other for the air intake. The problem with that design was that one of them was jammed into the air guide under the engine. It never got replaced properly when the air guide was removed, usually just lying on the top of the air guide.

      --
      Keeping it running is better than buying new



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    posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

    Does the ambient temp gauge read accurately before the engine warms up?

    A similar issue happened in our 2000 V70.

    The ambient temp sensor in this V70 is held in place by a small plastic bracket located in the right front vent/small grille, mounted low on the front valence. (Where fog lights go in some models but not ours).

    The bracket broke, and the sensor was hanging loose by the wire only, closer to the engine bay where it's hotter. Temps were reading at least 20 degrees higher once the engine was hot. It read accurately before first engine start of the day.



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      posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

      In warm weather, my temp sensor will routinely read 20 or so degrees hotter as well, either because of radiation from the ground or because of the engine heat.

      Good to know it isn't just a design flaw and that my temp sensor is that little wire dangling under the car. Soon as winter is over I'll finally affix it to where it ought to be.
      --
      ------



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        posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

        Yothere,

        I am pleased to know, my experience with my ambient temperature sensor is not isolated. When I get it "squared away" I will post the final chapter in my saga.

        Huugh



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      posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

      Robert,

      Thank you for your reply. Whether the engine is cold or warmed up has not impact on the temperature reading being elevated about 20 degrees. If I recall correctly, the temperature sensor either has a metal bracket that supports it, or snaps into a pre-drilled hole. I do recall it is not secured by a plastic bracket. When I get this "fixed" which I hope I do, I'll post the final outcome of what solved the problem. It is a nuisance for now. I just appreciated being able to look at the dashboard and immediately be apprised of what the ambient temperature was in the moment. The car is over 20 years old, so I have to cut it some slack.

      Hugh



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    posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

    It's only 25 years old. Probably the wiring rather than the sensor.

    You don't have to replace it NOW, it is not a critical part.
    Wait until it is warm and dry to find it, unplug it, clean the connector, and test it. If it still doesn't work, look around for a used one.
    --
    Keeping it running is better than buying new



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      posted by  someone claiming to be on  Wed Dec 31 18:00 CST 1969 [RELATED]

      Klaus,

      You are the voice of reason. I actually think I have a spare temperature sensor somewhere in my garage (maybe even two - a friend gave me one off a parts car). I had a similar problem on my 1999 V70 AWD XC wagon, and a new temperatures sensor did not fix the problem, so I learned to live with the temperature discrepancy and put aside the new sensor. You have to learn to manage your expectations sometimes.

      I will follow your advice and hold off until the weather improves and I can approach this issue in a more friendly environment.

      Hugh



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