try slapping the dash. it worked for me!
its most likely a corroded or loose connection but bulbs do burn out.
dealers can supply a special tool to remove the guage cluster its easier than using a screw driver to get it out.
good luck,
adam

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87 300E
BLACK GOLD WITH CREAM INTERIOR, SPOILER, AIRDAM
CLEAR MARKERS

87 420SEL
BRONZE WITH CREAM INTERIOR