Yanmar Tachometer Bouncing . . . Replacement ?

[akio.kanemoto]

Originally Posted by delmarrey

One side is suppose to go to ground and the other to the tach. The tach has a power input and output to the sender. It is a reed switch that is magnetic and counts the teeth on the fly wheel, which sends the number of teeth to the tach computer and actuating the needle.


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Thanks for this, greatly appreciated.

The interesting thing is that your and Gord's diagrams show one leg grounded whereas the official Yanmar service book doesn't.

Can I ask where this diagram came from and why it is more accurate than the Yanmar manual?

[bill good]

The tacho input was not earthed in the Yanmar loom but the DC supply earth to yours was prob. the fault & by supplying the DC side of things by earthing the black wire you got it working!! Most of the faults are on the engine side of the looms as the wires become brittle with heat age & oil. The Yanmar plugs & sockets are not the best for long life. (I live with two old 1GMs same loom)

Regards

[delmarrey]

Originally Posted by akio.kanemoto

Can I ask where this diagram came from and why it is more accurate than the Yanmar manual?

It came from here >>>> Troubleshooting Teleflex Tachometer Gauges

Which is Teleflex gauges.

According to the 3GM30 drawing the body on your sender (item #8) is the ground and the two wires goto the tach "P" terminal (item #10).
A bit different I would say.

.

[Bud McCall]

I had a problem that you are describing. I was turning the starting Batt off after starting and that was causing it.

[mglonnro]

Hello thread from twelve years ago!

I have a Yanmar 4JH3-HTE and wondering whether the following is a normal fail and whether the likely culprit indeed is corroded cables?

- Tachometer starts perfectly normally, and works perfectly normally for maybe 30 minutes or so.
- Then, it suddenly jumps up from let's say 2000 RPM to 4000 RPM and stays there. Ie starts showing about 2x the real values.

Is this something someone else has experienced?

[GreenWave]

Have not experienced that exact same symptom but have had similar flakiness. Likely when your circuit and wire heats up it causes that fluctuation. 99% of the time this is probably a bad or corroded connection.
1) Inspect, and remake your harness connections if possible. At a minimum spray CorrosionX into the harness connections and let sit overnight.
2) Inspect your conections in your panel; remove and clean any related to the Tach. Use CorrosionX and some emory cloth if needed.


I used this same approach to bring a "dead" Tach back to life just a few months ago.

[mglonnro]

Originally Posted by GreenWave

Have not experienced that exact same symptom but have had similar flakiness. Likely when your circuit and wire heats up it causes that fluctuation. 99% of the time this is probably a bad or corroded connection.
1) Inspect, and remake your harness connections if possible. At a minimum spray CorrosionX into the harness connections and let sit overnight.
2) Inspect your conections in your panel; remove and clean any related to the Tach. Use CorrosionX and some emory cloth if needed.


I used this same approach to bring a "dead" Tach back to life just a few months ago.

Thank you!

[capt jgw]

I've trouble shot a lot of things like this by temporarily running a complete new wire. If that makes the problem go away you know the fault is in the wiring. Even with all the connections good there still could be a chafed or other bad spot in a wire someplace where you can't see it.