FYI, my temp gauge was not displaying anything and the background light worked okay. I ruled out the sensor by testing with a 3.3K Ohm resistor and still nothing on the LED. I purchased a used LED display on e-bay for about $30 (found it under "124 display"). Swapped it out in about 2 minutes. Now it works fine. Must have been the LED display.

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1993 400E, 256,000 miles (totaled)
1994 E420, 200,000+ miles
1995 E420, 201,000 miles