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Old 07-01-2013, 00:53   #1
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Tachometer not working

I have a 3GM Yanmar diesel engine in my 1994 Caliber 35. I had to change a filter and bleed the engine to get it going again. The tachometer stopped working after that. I wonder if I damaged the sender while working on the engine. Has this ever happened to anyone? What did you have to do to fix it?
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Old 07-01-2013, 01:39   #2
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Re: Tachometer not working

Some diesel tachs run off a wire from the alternator, when my alt belt gets loose I know because the tach gets funny. 1970s westerbeke, yours might be different.
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Old 07-01-2013, 01:41   #3
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Re: Tachometer not working

Our tach runs off the alternator and will stop working when the batteries are fully topped up. You may have just run the engine long enough to fully charge - run the fridge long enough to get your beer cold and the problem might just take care of itself.
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Old 07-01-2013, 01:43   #4
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Re: Tachometer not working

There is an earlier thread on Yanmars with this problem.

IIRC there is a sensor that attaches to the housing and senses the teeth in the flywheel. That can back off and fail to read.
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Old 07-01-2013, 02:29   #5
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Re: Tachometer not working

Maybe this will help. Yanmar Tachometer Bouncing . . . Replacement ?

The thread deals with a tach issue on the same make of engine. Some real answers from CF old timer Gord. Sounds to me like you may have knocked a wire loose when you were working on the engine. Sometimes though it is just a coincidence when something else breaks. If you don't have the manual you can find it at http://www.yanmarmarine.co.uk/pdfs/o.../128270-4E.pdf
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Old 07-01-2013, 03:09   #6
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Re: Tachometer not working

Your tachometer receives information form either the alternator or a dedicated tachometer sender on your engine block near the flywheel.

If you have an externally regulated alternator the tachometer receives information from the alternator. Look on the back of the alternator for the field and stator wires. They are usually blue and white. If they are there check their condition for corrosion and continuity. (wires can break inside the plastic connectors).

If you do not have the blue and white wires at the back of the alternator, look for a pair of wires that are orange and blue/red (Yanmar colour code). They will be attached to the tachometer sender. You may have knocked one loose.
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Old 07-01-2013, 10:07   #7
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Re: Tachometer not working

Had the same thing happen to me..check your wiring harness connections around the alternator leading up to the panel.

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Old 07-01-2013, 10:16   #8
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Re: Tachometer not working

Quote:
Originally Posted by LJH View Post
Your tachometer receives information form either the alternator or a dedicated tachometer sender on your engine block near the flywheel.

If you have an externally regulated alternator the tachometer receives information from the alternator. Look on the back of the alternator for the field and stator wires. They are usually blue and white. If they are there check their condition for corrosion and continuity. (wires can break inside the plastic connectors).

If you do not have the blue and white wires at the back of the alternator, look for a pair of wires that are orange and blue/red (Yanmar colour code). They will be attached to the tachometer sender. You may have knocked one loose.
Check that connection that plugs in the back of the alternator. And yes sometimes the tach wont work depending on the state of charge etc....
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Old 07-01-2013, 12:39   #9
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Re: Tachometer not working

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Originally Posted by hpeer View Post
There is an earlier thread on Yanmars with this problem.

IIRC there is a sensor that attaches to the housing and senses the teeth in the flywheel. That can back off and fail to read.
That's correct. Also, corrosion or a bad sender or tach are possibilities.
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Old 07-01-2013, 12:58   #10
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Re: Tachometer not working

Where does the 3GM tach get its' signal? Isn't that a popular older engine that someone here wold know this answer by now?

Both my boats had Yanmar engines (but not the 3GM) and have had tach problems. Both also got the tach signal from sensor mounted on the flywheel housing. The first was a corroded wire at the sensor, the second it was the tach.

Since the problem didn't happen till you worked on the engine the cause is almost certain to be a loose connection or a flayed wire that is about to part way.
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Old 07-01-2013, 13:01   #11
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Re: Tachometer not working

Thanks all for the help!
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