Believe that the '85 tach unit is different from the earlier, ie. 82-84, years. The earlier units have some electrical items in the little miniature 'trash can' located on the drivers inner front fender well. Someone else may be able to suggest where the electronic parts reside for 1985.

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1961 190Db retired
1968 220D/8 325,000
1983 300D 164,150