Jumping tach needle

[Incubus]

This might be a silly question, since we are talking about a 27-year-old tachometer that sat unused for 15 years or more, but the needle on my tachometer pretty much jumps all over the place when I am riding - yes, riding - my 79XS F. It is practically useless for its designed purpose. I don't really care much about this tach, since I have a replacement I can put on, but I wondered if this could be a symptom of something else I should be looking for. All my other tachs are cable driven, so I don't know what to make of the jumping needle on this tach.

Patrick

[wingnut]

Clean connections

Try cleaning all of the connections from the alternator. The tack pickis up its signal from there. That has worked for some folks.

[jeffe]

My understanding is that the tach gets its signal from the alternator. Not quite sure how. One of the Guru's can help you with the wht. When the regulator/rectifier started to go bad on y 78E the tach needle jumped all over the place, like you described. Soon after that the reg/rec went out. When I replaced it with one from Geezer it worked much better. Just one of the side effects I guess.

[jeffe]

Oh by the way. It was first recomended that I try cleaning all the connections that have to do with the charging system first. In my case it did not help. But it could be a start for you

[prometheus578]

I'd turn on a turn signal and the tach needle would blink, too!. Bad connections all over... fuse box, too... but a different regulator made the biggest difference.