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Old 03-06-2019, 05:14   #1
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New Alternator / No Tacho

Any of you guys help here? I've got one of those marginal cases that needs another angle that I'm not seeing right now.

I just installed a new alternator system on my 4JH3-TE (CMI-80-ERH plus Balmar ARS-5).

It's all in and providing power nicely.

However, I've now lost my tacho (no reading at all on the dial).

Just to avoid any misunderstanding, this should not re related to the stator connection on the alternator itself or the tacho output on the ARS-5. The 4JH3 has a tacho driven by pulses from a flywheel sensor which was working 100% previously with the Hitachi alternator installed and the stator wire not connected to anything.

The ground connection from the alternator and the ground connection from the tacho sensor both meet at a bolt on the engine block.

I accidentally left off the connection from the alternator and that restored the tacho pulses (yes, I know that's bad but it was very short and the alternator must have been grounding via the case and engine block). As soon as I reconnected the ground wire, the tacho stopped again.

I'm guessing this is some kind of noise on the ground line of the alternator overwhelming the signal from the tacho sender.

Mainesail probably knows most about this stuff (are you lurking here?) but any suggestions are welcome.
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Old 03-06-2019, 06:49   #2
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Re: New Alternator / No Tacho

"Electrical" chapter from the Yanmar service manual
http://sagaforumet.com/yanmar-manual...kapittel_9.pdf
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Old 03-06-2019, 07:00   #3
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Re: New Alternator / No Tacho

Thanks Gord,

I already had that and it confirms that the pulse source for the tacho should be the 1V p-p signal from the flywheel sensor NOT the stator output on the alternator.

Still have the same issue, If I directly connect the alternator to the ground bus, I lose the tacho.

Duncan
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Old 03-06-2019, 07:40   #4
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Re: New Alternator / No Tacho

Feedback: OK, /i think I nailed this one. Looks like the wiring activity close to the tacho sensor had disturbed the physical connectors to the sensors (I didn't realise they are push on blade types).

I gave them a good wiggle and the tacho is back on now.

So to help anyone else going this way, on 4JH engines at least, don't worry about the tacho sensor wiring, it isn't connected with the alternator at all.

Duncan
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