Tachometer needle "dips" frequently - Page 2 - SailNet Community
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post #11 of 19 Old 05-28-2009
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This is a timely post for me. Last night for the first time in the six years of ownership I notice my tach speed slowly raise to the true engine speed on my boat. I've been thinking about the electrical connection I have to fix this weekend but now believe a more likely culprit is a loose belt spinning the alternator up slowly.

It never accur to me that the tach signal was coming from the alternater.
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post #12 of 19 Old 06-29-2009 Thread Starter
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Update

Hi all,
Well, the symptoms have changed a little from my first post about this subject. Not sure where this leaves us, but here we go...

First, here's the pic again for reference:


The part highlighted in red, which I call the "clicker", used to flip from plain white to a black line every second or so whenever the key is on. It's now stuck on black line (though you still hear the "click"), and the hour meter is also stuck.

Here is what happens:

The "clicker" makes the clicking sound, but does not rotate. You can see it try to rotate (moves a tiny bit), but it is stuck.

At the same time, you can see the hour meter, which is now at 1519.9, try to rotate to 1520.0, but it is also stuck. Again, you see it try to move (so there is power), but it doesn't actually rotate. It tries to move in unison with the clicker.

Sometimes I still get the tachometer needle "dip" with this behavior, other times not. I checked all the connections on the back of the tach, and everything seems OK. I tried checking connections at the alternator end of things, but am still figuring out the wiring since my alternator is not original and there's a separate voltage regulator in the mix (also not original), so the wiring diagram in my manual doesn't match my boat exactly.

So, is this still some sort of electrical/ground problem? Or is the hour meter just bound up (mechanically)?

Any ideas on next steps to figure this out?
Thanks,
J

1984 Sabre 34 Mk I
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post #13 of 19 Old 06-29-2009
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In the picture you're showing 1430 or so hrs - you now say it's stuck at 1519... does this mean that the hour meter DOES increment some of the time? Or is it just an old picture?

What you describe does sound like a physical problem with the hour meter's integrator - perhaps you have a broken or missing gear tooth. As to sorting that out it seems to me you'll need to remove and open up the tach/hr meter to investigate.

Ron

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post #14 of 19 Old 06-29-2009 Thread Starter
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Quote:
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In the picture you're showing 1430 or so hrs - you now say it's stuck at 1519... does this mean that the hour meter DOES increment some of the time? Or is it just an old picture?

What you describe does sound like a physical problem with the hour meter's integrator - perhaps you have a broken or missing gear tooth. As to sorting that out it seems to me you'll need to remove and open up the tach/hr meter to investigate.
It's an older pic from before we bought the boat. Then we sailed her from CT to MD and put a good number of hours on during the trip. The hour meter was working normally until 1519, then it stopped. Thanks Faster...

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post #15 of 19 Old 06-30-2009
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We had a similar issue with the Alternator on our Perkins 4-108. It proved to be a regulator issue and occurred when the batteries were fully charged. The regulator would turn the Alternator on and off as it "alternately" detected the draw down on the batteries and then the full charge. If that’s the problem it may be defeated by activating some power draws on the boat—lights, fans, radar etc. We ended up replacing our regulator with a Balmar AR-5.

As for the hour meter and the “clicker”, they may only be powered when the field current is applied to the alternator. I suspect the “clicker” window is an indicator that power is being applied to the alternator. Obviously, the hour meter should be on a different circuit entirely, one that is active whenever the engine is operating.

FWIW…

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post #16 of 19 Old 06-30-2009
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Buy and install a new unit.

The clicker is the winder and something in the gearing is not working and the line is showing that the hour meter is on.

If that does not fix your problem then run the checks sugested.

Rick
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post #17 of 19 Old 06-30-2009 Thread Starter
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Quote:
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Buy and install a new unit.

The clicker is the winder and something in the gearing is not working and the line is showing that the hour meter is on.

If that does not fix your problem then run the checks sugested.
Hey timebandit--when you say buy and install new unit--which piece are you referring to? The whole tach or just the hour meter parts? Other?

I'd like to avoid buying a whole new guage, unless I really need it.

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post #18 of 19 Old 07-01-2009
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If you can get it apart and the hour meter is available seperate just get it(hr meter) but I doubt it comes seperate.

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post #19 of 19 Old 07-01-2009
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I think Timebandit is probably right, the hour meter is shot and I doubt you could get a new one without buying the whole tach, Motorola should be able to tell you though. I have a Volvo instrument panel and a separate Hobbs hour meter, and when the hour meter clicks all of the gauges "dip" a little. I tried another hour meter and it does the same thing. All connections are tight, just the nature of the beast I guess.

John
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