if the fuel gauge does an occassional odd movement also, I would tend to believe that there is come oxidation or breka down at the gauge cluster. The temp and fuel gauge have a lot of circuitry they share on the circuit board and the ground they use is the same. For know that is probably something you will have to live with. It can require opening and dissassembling the cluster to clean up all the connections. Lots of good mechanics know nothing about instrument clusters and they dont want to. they are tempermental and time consuming to work on with no guarantees of sucess. Most will tell you there is nothing that can be done, it is typical, or buy a new or salvage clsuter and try that. Not great options.

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Christopher Henkel
1990 190E 2.6 - Arctic white SOLD
1986 190E-16v - Blauswartze
1993 300CE - SOLD
2003 W208 CLK 320 Cabriolet - Magma Red