No problems so far. As I'm sure you know, the '85 has an electric tach so I guess you'll have to try tracing from the tach backwards. You may also want to take a close look at the "mother" board on the back of the instrument panel since I've heard stories of some of the dash instruments acting up if the conductive tape on the circuit board starts to delaminate.

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LRG
1987 300D Turbo 175K
2006 Toyota Prius, efficent but no soul
1985 300 TDT(130K miles of trouble free motoring)now sold