Tachometer

[Johnnymalo2]

I have a Yanmar 4JH3HTE and my tachometer has started to hunt for the correct revs and is getting poor results any advice

[JPA Cate]

A loose wire or corroded and/or loose connection, trace from alternator to tach, if it's an electric tach. I'd still look for a loose connection, even if it's a mechanically driven tach.

[Johnnymalo2]

Thanks for swift reply
All wires look OK but I guess it's just a case of pulling them apart and checking for corrosion

[JPA Cate]

Hey guys,

The OP could use more help here than I have the knowledge to give!

[River Cruiser]

Originally Posted by Johnnymalo2

Thanks for swift reply
All wires look OK but I guess it's just a case of pulling them apart and checking for corrosion

Get a can of electrical contact cleaner & use it when you pull the plug connections apart. Good luck

[MARC D]

OP, Do you have the electronic type Yanmar panel (type A or B) ??

[sailorchic34]

Sounds like corrosion too me. clean the connectors with a small file or emery board. I need to do that every 3-4 years it seems with my 3gm

[GordMay]

Greetings and welcome aboard the CF, Johnnymalo2.

[Johnnymalo2]

Type B panel
Slow responses as my Internet access is limited here in Maine

[rodney_k]

JM2,

If your 4JH3HTE tach is like the one I have on my 4JH2E, the signal for the tach comes from a magnetic pickup that literally "counts" the teeth on the flywheel going by when the engine is running. My tach was hunting too. Tapping the front of the tach would sometimes stabilize the reading.
On the rear of the tach there is a range switch that selects a range of teeth on the flywheel to allow the tach to be used with various engine models. On my tach, merely working the switch through its range with a little squirt of contact cleaner would fix the tach for several weeks.
There is also a calibration pot that gets dirty too. A squirt of contact cleaner and working the pot through its range will restore stable readings. Caution, you must remember or mark the exact location of the pot's position or your tach's calibration will be off.
I finally disassmebled the tach, removed the range switch, and soldered a wire jumper in place of the switch. Problem gone.
If you are not familier with soldering techniques on small printed circuit boards and small components, I would not recommend taking the tach apart.

[MARC D]

I have the same tach and last winter it's started to go on and off. Also, the digital hour meter was blinking. Of course, I first suspected corroded wires/terminals. I cleaned and checked everything, to no avail.

Than I described these symtoms to a Yanmar mechanic and he immediately suspect a ''frozen brain''. He then told me how to reset the electronic circuit with the tiny pushbutton switch located behind the tach. And this did the trick.

Unfortunately, I can't remember the exact procedure but you certainly can ask a Yanmar serviceman. This little button is also used to do fine calibration of the tach and range selection, if I remember well.

Good luck,
Marc