What could be the problem ?

My instrument cluster on my 97 e320 has only one light lighting up at night : only for temperature.

I have checked the balbs and they are o.k. but will not light up.

Your help greatly appreciated

Thank you

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2008 ML320 CDI
2007 GL320 CDI
2005 Audi A6 (sold)
2001 E320 (sold)
2004 lexus RX330 (sold)
2004 Honda CRV (sold)
93 190E 2.6 (sold)
97 E320 (sold)
2000 Honda CRV (sold)
91 350SD (sold)
90 E300 with amg body kit (sold)
83 300sd aqua marine (sold)
81 300sd dark blue (sold)
81 300sd gold (sold)
81 300sd brown (sold)