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-   -   Tachometer problem (http://www.sailnet.com/forums/gear-maintenance/45724-tachometer-problem.html)

okapi3 08-05-2008 03:38 PM

Tachometer problem
 
Hi all,

The tachometer on the cockpit mounted panel for my Yanmar 3GM30F (on my '88 PSC 31) just stopped working. Needle doesn't move at all. The engine is running fine. The engine is rebuilt but the tach is probably the original 1988 deal. I looked around behind the panel for a fuse but didn't find one. Does anyone know if there is a dedicated fuse for the tachometer (a simple fix would be nice). If not, any other likely culprits or troubleshooting suggestions before I buy a new one? I don't have a lot of engine experience, but I'm learning--one broken part at a time. Thanks in advance,
Paul:confused:

sailingdog 08-05-2008 05:51 PM

Welcome to the wonderful world of boat ownership... There are a few PSC31 owners on here, who I'll leave the question to, since I'm not familiar with the setup on it. :)
Quote:

I'm learning--one broken part at a time

4e14n9s 08-05-2008 06:39 PM

Tach not working
 
I had the same issue on my H310 2GM20F. After research found that the reset is to hold the bush button on the front of the tach when turning on the power. This is a reset. You may have different setup, but, cheaper to try than buy.

Omatako 08-06-2008 05:02 AM

Hey paul

I don't know if this will help or not. I have had a similar problem with mine but I have a 4 cyl Yanmar so don't know if they're the same but like another post said, it's cheaper to try than buy. Here's what I found:
  • On mine the tacho is driven by a magnetic pulse sensor on the flywheel. Check around the bell housing and see if there is a unit that has two wires from it on the bell housing. They may have come off.
  • If they are still on, you can put an ohm meter across the sensor and should get a reading. The technicians who eventually declared my tacho DOA said that any reading is good news (they're either right or knackered) and no reading is obviously not good news.
  • On mine we had a voltage spike and the tacho itself got toasted. If you had a similar spike, my condolences, your tacho is history.
  • The cost of a new Yanmar tacho (mine has a built-in hour meter) is about $290
Good luck

Andre

sander06 08-06-2008 06:07 AM

The first thing to check on anything run by electricity on a boat is the ground. No ground, no work.

okapi3 08-07-2008 12:30 AM

Thanks for your various suggestions. I will certainly try the simple things first. As for a voltage spike, I can't think of having had one, but shortly before the tach stopped working I did burn up my alternator belt and replace it. Am I correct in thinking that the tach leads attach to the alternator somewhere? In that case they may have gotten pulled off in the tussle.

Question for Sander06: How do I "check the ground?" (I'm just posting this question to help others out there who might not know the answer, not because I would be so ignorant myself;)).

sander06 08-07-2008 05:59 AM

Just about every gauge I've ever seen has a green wire coming out of the back of the gauge with a little "G" beside it. Run a wire from that little green gauge wire directly to the negative terminal on your battery. If it works, that's the problem. I've got a couple of pieces of long wire with alligator clips attached at each end just for that very purpose. I just used it the other day to track down a shorted out wire I managed to create installing some light fixtures.

You're learning about fixing boats exactly the way most of us have done. Keep up the good work and look for the simplest solution first. You're well on your way to becoming an "expert"!!

Good luck.
Steve


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