Yanmar tach dropping out

[svjoyeux]

I am having problems with the tach on my 2004 Yanmar 4JH4E dropping out. When we repowered (List Marine in Sausalito did the repower) we installed the Type C instrument panel. In 2011 the hour meter in the tach stopped working and I installed a Hobbs meter. I have an Amptech 125 Amp small case alternator (installed in 2004) and a Xantrex XAR smart regulator. About 3 years ago the tach started either dropping out (95%) or reading 1200 rpms high (5%) when the battery bank was fully charged. I have tested the alternator, which is OK (I think) and the XAR which also seems OK. The pros I've talked to have told me it's the voltage regulator, but I put in the spare and the problem persists. There are a lot of variables to eliminate, unfortunately. When we finally stay put for more than a few days I will probably have the tach tested and calibrated but for now have to live with this.

I wonder if anyone has any ideas about why this is happening and/or test suggestions to help me eliminate some of those variables.

Thanks in advance
Rob/Joyeux

[witzgall]

This may be normal, expected behavior, depending on how that charge controller is working. If the batteries are charged to a point, and then the controller drops to a no charge, or lower voltage float charge, the alternator may stop putting out any charge. The tach gets its signal from the output from the regulator. Since the regulator is no longer calling for charge, the tach drops out.

Think of it as a poor man's battery full indicator.

If you read the instructions for your regulator, you should be able to see if that is what is going on, by looking at the settings and comparing it to the voltages you are seeing on the boat.

Chris

[Sailmonkey]

If your tach is driven from the alternator, then this is normal behavior for those times when the batteries are full.

Ours does this when the batteries are full and the solar is keeping the voltage high. The solar float point is slightly higher than the alternator, so the alternator is turned off by the regulator to try and control the battery voltage

[svjoyeux]

Thanks for the quick replies. I agree with the 1st two replies. We have both solar and a wind turbine. I've taken to stopping the WT if we're having to motor. What I don't understand is why the tach sometimes reads 1200 rpms high. Instead of simply dropping out, it fluctuates wildly a few times then goes up to the high reading. In those instances when we finally turn off the motor, the tach drops to 1200 and stays there in until I cycle the ignition. When the batteries are full the monitor still shows a few amps going in, which I surmise is the solar. I'm going to try dropping the amp output of the regulator to 90% and see what happens.

[Sailmonkey]

Try running something high load....like a 60 watt light bulb through an inverter. I'll bet your tach stays alive.

[boatman1]

It's my experience that the connections in the wiring harness on Yanmars (and perhaps all engines) can be problematic. I expect that wiring the tach to the alternator with no intermediate connections might fix the problem.

[sailon46]

When my Yanmar did exectly the same it was a small drip of seawater from the elbow straight down to the sending unit of the tach on the flywheel. Big a.s midterm but problem solved.
Maybe it is your problem FYI
Ernie on the Mary Jane

[subie]

On my little Yanmar GM10 I experienced more or less the same symptoms with the tachometer. On my boat in the wiring harness there is a multiplug. I unplugged it,dried and wiped it and sprayed with silicon. Instant fix for me. Hope yours is also something so simple.

[FULLCIRCLE331]

I had a similar problem but not just the tack also the voltmeter and ampmeter. Never full understud the problem but a Volvo mechanic told me it was either the alternator or a ground. I swapped out the alternator and the problem went away. Check the alternator output when the tack drops out. I also have solar but the problem didn't always occur at full charge.

[TheOffice]

If they all drop out wiggle the fuse holder on the instrument panel.