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Old 10-03-2002, 02:23 PM
James N. Pinto
Posts: n/a
Lightbulb OTG Issues

I have a 1989 260E and have a problem with the OTG (outside temp gauge). The display reads 123 degrees all the time. It worked when I bought the car in 1998 but went haywire shortly after. I traced the sensor (from under the licence plate) and it appears to go into the fuse box unless I got my lines mixed. Does anyone have any diagnostic / replacement tips and or where to get a replacement sensor assuming that's the problem.. Here in Vermont an outside sensor comes in handy on those -20 winter days
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Old 10-03-2002, 03:03 PM
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Join Date: Aug 2001
Location: At Sea
Posts: 1,729
OTG thread
1993 300e-2.8
- gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"
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Old 10-03-2002, 04:28 PM
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Join Date: Mar 2001
Location: Evansville WI
Posts: 9,616
You can unplug the sensor (yes, it goes into the fuse box) and if you have a resistance substitution box, plug in values that will give the proper readings. The resistance values are found in the repair disc.
I would recommend getting the part here at MercedesShop (PartsShop or Fastlane) because the business you do here help support this site.
One thing to remember is to NOT shorten the wiring of the new sensor, the resistance is critical enough that shortening the line will affect the sensors accuracy. Wind up the excess wire and leave it in the fuse box.
Given your problem, I would assume it is a bad sensor also.

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Old 10-03-2002, 04:51 PM
Join Date: Mar 1999
Location: Tucker, Ga USA
Posts: 12,153
The resistance value at 32F is 9800+- 100 ohm & at 104F is 1600+-100 ohm, if you cut 5 feet from the wire you might make 1/2 ohm change. DON'T think that 1/2 ohm will make any difference in reading!!
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Old 10-04-2002, 05:52 AM
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Join Date: Dec 2001
Location: Yorkshire England
Posts: 70
3 wires from the sensor go into the fuse box. 1 goes to a fuse, for 12v, and the other two are paired together in a connector, with the half that goes into the dashboard probably having a brown and a green wire. You'll find the connector in the bottom of the fuse box, under the fuse tray.

Hope that helps


1994 E200 Wagon 111,000 k miles
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