Yanmar 4JH4 hte Tach

[Capt Dash]

Our Yanmar 4JH4 hte tachometer suddenly jumps to and stays at full rpm & hour meter stops. If we kill the engine & restart, both rpm & meter will function normally until something triggers it to go whacko again. Alternator is a Yanmar 80 amp. Engine hours 2550. Any ideas? Faulty Gauge?

[Avionics_Joe]

It's probably a faulty gauge. Instead of stopping the engine, try powering down the panel, wait a couple of seconds, and power it back up. If that works it's the panel.

Also, try unplugging all the connectors and plugging them back in.

[Capt Dash]

Thank you for the help. Wire connections seem good. Was unable to test the panel shut off yet because tach was stable all day while running. Will attempt that if it goes erratic again …..next day we move.

[skipperpete]

This is just a question…..Can a solar array affect the output of an alternator by giving its inbuilt regulator a high voltage signal that causes the alternator to stop charging and the tacho to stop counting the frequency?

[Capt Dash]

That’s beyond me, but both days when this occurred, we’re overcast with low solar gain. We’ve had active solar for six years now.

[skipperpete]

Originally Posted by Capt Dash

That’s beyond me, but both days when this occurred, we’re overcast with low solar gain. We’ve had active solar for six years now.

Thanks, that rules out that possibility.

[Avionics_Joe]

Originally Posted by skipperpete

This is just a question…..Can a solar array affect the output of an alternator by giving its inbuilt regulator a high voltage signal that causes the alternator to stop charging and the tacho to stop counting the frequency?

No, the tacho will keep working. Even if you unplug an external regulator the tacho will keep working.