My outside ambient air temp sensor is probably fried as my car has always show -45 deg C in dash display. If I fix it (ie- replace the sensor or such), do I gain anything? Any performance increase? Less wear/tear on any system? I have a euro-spec '93 2.5L TD stationwagon.

FWIW, in my BMW back in the states, the outside air temp drives the climate control system so it has a pretty big effect on the car. In other words, when it's 100+F in south Texas, the car thinks it's -40F so why would you need the a/c? You have to put the a/c system on max cool and you loose the self-adjusting temp. I think it affects a little on engine performance also, but haven't verified.

The ambient air temperature sensor in the front bumper is only for the display on the dash. It has nothing to do with the climate control, which has its own sensors.

Your display reads -45C because the sensor has been disconnected from the display. This could be a bad sensor, an unplugged connector, a broken, frayed, or otherwise damaged wire, etc. Trace the wire from the sensor all the way back to the display. (I say this as if it's a trivial job. It isn't, of course, it's a PITA, but that's what you must do.

Also possible but less likely is a bad display.

Jeremy

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Very good response Jeremey. Not wanting to hijack this post, but I practiced on a W126 in a unk yard to fix my SEC years ago. Somehow the harness got stretched and weakened a lead wire to the display.
Sold the car, but realized others may encounter this problem. So I began removing the outside temp displays from the W126 chassis. I have several available in both fahrenheit and celcius.
Takes about an hour now that I know what to do and where to cut the harness out f the cars main wiring.

Also found some people with the W123 chassis interested in installing the complete system into their cars. The space for the display is already in the instrument cluster.

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Thanks Jeremy. I figured the sensor was only for looks. I found the sensor location when I installed my new plates last month when I bought the car. The dash display "usually" reads -45degC but sometimes it is blank. As long as it doesn't affect anything, I'm not going to worry about fixing it.

Now just have to figure out if my aux fan is working. Still playing with it but if I can't get it to work, I'll toss up another thread.

Rex

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1993 E250 2.5L TD 230,000 kilometers
Vicenza, Italy