You don't mention the year of your car, but an 85 SEL has this> Fuse 12 8A white Stop-turn signal lamp, instrument cluster, diagnostic, warning monitor term. 8, cruise control, tachometer. Most MB cars of this vintage have some bulbs and unrelated components on the same circuit as the instrument cluster, although the particular fuse may vary from model to model. These other components could be the culprit.

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