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Old 07-08-2002, 08:37 PM
Keith Lucy
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Unhappy Can anyone PLEASE help me fix my external temperature sensor?

Can anyone PLEASE help me fix my external temperature sensor?
It's really bugging me whenever that display comes up at -36F. I cannot find any evidence of the sensor at the bumper end, but know that it must have had one because of the internal display. If anyone could please describe to me, how the wires that come from the sonsor are routed, where they eventually connect to and their color, I would be deeply appreciative.


P.S. It's a 1991 560SEL
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Old 07-08-2002, 08:52 PM
Gilly's Avatar
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Join Date: Mar 2001
Location: Evansville WI
Posts: 9,616
The temp sensor screws to the back side of the front license plate frame. The wire goes through a hole in the bumper, then to the drivers side around the inner part of the fender where it meets the wiring harness, follows the harness into the bottom of the fuse box, where there is a connector where it connects to a short harness to the instrument cluster. If you replace it, don't change the length of the sensor harness, as it will affect the accuracy of the new sensor.
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Old 07-09-2002, 10:31 AM
yal's Avatar
yal yal is offline
Join Date: Oct 1999
Location: New York, Long Island
Posts: 2,704
Some links that might be of some interest to you regarding the temp guage.....

87 300e outside temp gage

outside temp LCD
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Old 07-10-2002, 05:39 PM
Keith Lucy
Posts: n/a

I tested the cable and display with the 3K resistor and that works fine. The sensor looks like it fell off and was dragged for a few thousand miles. I have parts on order from Newark and expect that that will get it working. I bought the Fenwal sensor, for $9.62 each. I bought two in case I screw it up.

Thanks to all that helped. This board is great.
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Old 07-10-2002, 07:15 PM
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Join Date: May 2001
Location: Florida
Posts: 1,105
benzmac: interesting comment reguarding the length, i must have just gotten lucky in what i did i suppose. I didn't have it originally in the car, so i installed it into my car along with the cluster it came with, and used speaker wire for the wires all the way around, i ended up routing it through the firewall and around a whole bunch of stuff, so i'm sure it has a much differant than factory length. My temp is consistently withing 1-2* of actual, unless i'm sitting in traffic or at a light, then it says it's hotter than it is. This 15 year old sensor is 10 times more accurate than my g/f's 2001 pathefinder's, even with how rigged mine is. Go figure!
83 300SD.......sold
96 integra SE....sold
99 a4 quattro....sold
2001 IS300.......sold
2002 330i.........current.
2004 highlander limited....current.
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Old 07-10-2002, 11:08 PM
Keith Lucy
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Resistance of wires vs Thermistor

The thermistor used as the sensor has a resistance of 3000 ohms at 75 degrees (F) which, of cource, varies with temperature. The resistance of the wires used in routing would be on the order of 20 ohms. Even if you were to use double the original length and introduce 40 ohms total (an extra 40) you would introduce an error of 20 parts per 3000 or 0.67%. If the outside temperature were 75 degrees, and the sensor was perfect, your display would read 75.5 degrees (if it had decimal places).
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Old 07-16-2002, 11:55 PM
Keith Lucy
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All set

Got the sensor, and installed it yesterday. Although I think it's about 6 degrees high, it's working fine.

Thanks for all the help !
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