mad tack.

[zenboy]

getting the 86 280i ready for its winter sleep. decided to go for one last run just as im pulling into the driveway the tack. starts to swing up and down from 0to 7k this was all in the tack. the engine r.p.m.stayed constant.any ideas.cheers mike

[wedg1e]

Bad earth, loose fuse, grotty connection to an 'ignition' relay or ignition switch itself, instrument fault. Unlikely to be a bad signal from the distributor, but check it anyway. Remote chance it's the tacho itself but could happen.

Ian