Tach problem

[GWG]

Randomly, the tach on my Yanmar4JH5E is pinned at beyond the max--all the way over. The engine is running normally, and the voltage reading is normal. When I shut down the engine and restart, the tach shows the correct reading. This does not happen often, and there seems to be no pattern as to when it occurs. My guess is a loose wire somewhere. Anu suggestions?

 

[mayday]

My new 2ym15 started doing this as well (as well as the portion of the hour meter going blank) after extensive research I found it was a reasonably common problem that seemed to be attributed to some moisture inside the meter (third party not Yanmar) - appparenly you can take it all apart, dry and re-assemle. I haven't yet gone to that extent yet - I've found if you throttle back, turn off, re-start, that usually fixes the "problem". Once I found out the hour meter continues to count even if the display is missing, then I became less concerned.

 

[Maninita]

We have the same problem on our 4JH5E. I have fixed it by jiggling the connectors at the rear of the tach/panel or it has gone away when the engine is turned off and restarted, but no long term solution found yet.