Instrument electrical failure, Yanmar 4 LHA STP

[Yannis]

My tach stopped working while I was cruising back.
Actually all 3 instruments of stbrd engine.
I changed a fuse that is just behind them, under the fb coaming - you need a lot of goodwill and determination to fit in there - anyway, the instruments started working again ...until the fuse got burnt again, this happened three times.
Last time I noticed that right before it burnt I had bumped into a big wave and it was that abrupt boat movement that led to one or two momentary black outs of the instruments (the needles moved to zero, then back to normal then back to zero) until they stopped functioning for good.
My electrician suspects that this fuse thing is an after effect of some wire that when bumped or moved (by the wave motion) makes some kind of contact somewhere, he thinks of the snap plugs connecting those million wires on the engine side (there are 3 of them).
How do I find which one it is? And if it’s not there, where else should I look?
I don't want to even think having to rewire the engine...

[mike ohlstein]

Never change a blown fuse three times. Once the first replacement fuse blows, you know something is wrong.......

[Tony Meola]

Yannis

If there are only 3 points to check, it should be fairly straight forward. You can either redo each connection and hope that is it, or you can not follow Mike's advice and replace the fuse and wiggle each wire until you hit the jack pot. But Mike is right once you change the fuse, unless it is undersized, if it blows a second time, do not replace it for a third without fixing the problem.

You could also play it safe and try an ohm meter. The wire should have resistance, so with the power off if you attach the ohm meter to one end of the connection and can reach the other with the other end you should get an ohm reading. If you get a reading the wire should be good. Then move on to the next, once you get a 0 reading you hit pay dirt.

Now if you get really lucky, once you start tracing the wires from the fuse you might just find the gremlin since at times it is more obvious than you think.

Perhaps one of the electrical experts will jump in and help us out, with more options.

A short can be a bear to find.

[Bruce]

That 3 amp fuse comes off the ignition switch and feeds the instruments so the issue would be after the fuse which would be the instruments.
Look for moisture, chaffed wires, loose wires shorting or it could be internal to one of the gauges. Plug one guage in at a time till you find the one that pops the fuse.

[Yannis]

Bruce,

For simplicity in my explanation, I did not mention that after the second fuse was blown, the rev instrument was completely dead alright, but the oil pressure and temp gauges were not completely dead, they were showing a value at around 60% of what they would normally show.
Is this an indication of something? How can there be partial flow of current through a blown fuse? Or is it irrelevant?
Thanks.

[Bruce]

Yannis,
Without checking the fuse feed to those gauges with a meter for possible voltage, I can't answer. But some electrical guages will not zero when power is removed. There also could have been moisture, which can conduct Milliamps of current to the smaller guages but not enough to the tach.

Has the instrument panel been modified or any circuits pulled off the instrument feed?

You have the C panel, correct? Here is a link to the schematic for the C panel.

http://www.manualslib.com/manual/833908 ... ml?page=64

[Yannis]

Bruce,

Thank you.

Yes I have the C type. I’ll try to fit back there and take a look again...
I always say to widen the two flybridge side doors but so far ...nothing, damn it! I slice my ribs each time...

[Yannis]

Yesterday and today were the big days. We went twice to the boat with the electrician, to try to figure out what happened.
After multiple trial and error checks, he found two wires behind the instruments (inside the flybridge coaming), to be naked and making contact when agitated! He isolated them, changed the fuse, put some general order in the area and bingo. The culprit was found.
Bruce you were spot on, thank you.

The story: Four years ago, I got rid of my original compass to make space for the gps at the same location, at the top center above the instrument panel.
I had to find another location for a smaller dash type compass that would replace the original, so I removed the (useless to me) instrument that shows the rudder angle and placed the new compass at its hole on the panel. Little did I know that when you disconnect an instrument and remove it, you simply do not dispose of the cables back into the hole randomly, without isolating them...because a few years later they may make contact and burn the fuse while underway. Im glad there was a fuse up there because this prevented much more serious failure like... fire for example. Sometimes you can fix stupid and that was one of them.
Case closed.

[Tony Meola]

Yannis

I hope you do not work on electircal wiring at home.

[Yannis]

Never Tony!

Especially with 220v I cannot take any risks..., I turn on the water heater and I change the bulbs though. All by myself!



The newly discovered Egyptian mummy, as it's being pulled out from its resting place !! (my electrician)

https://imgur.com/a/8gQ1Nvq

[Carl]

Those pesky little wires...who would have thought they'd cause a problem just floating exposed around under the dash...on a boat...rockin, rollin and a pounding.

Glad you found issue...oh boy am I glad you found the issue.



You definitely got your moneys worth from that electrician!

[Yannis]

What’s interesting, though, is that before he tackled the under-the-dash area he looked inside the engine room, especially those multi cable strings that are allover...when I told him about the mouse visit I had, he almost tore the whole boat apart to follow those engine cables inside the pillars...you can imagine.
The next day he decided to go up at the bridge and the minute he put his head inside the coaming he found it. He also started shouting “who changed a meter on the dash?”...I was almost too scared to admit it was me.
You know, this kind of cable work you can do for days without necessarily having any guarantee that you’ll find the problem...
Like you said, oh boy, was I glad to solve this issue!

[Tony Meola]

Yannis

You learned two valuable lessons.

First, never ever invite a mouse onto your boat. They love to chew on wires. So do squirrels by the way.

Second, if you want to continue living a long life, never leave a pair of wires that are not attached to something functioning live and hanging loose.

You need to make a big donation to your local church, say few prayers and thank the lord.

You got off lucky.

[Yannis]

Tony,

You’re right, very lucky is the word.

Btw, we do not have squirrels! Possibly because the tallest tree in the islands is parsley!

I have a friend, seasoned sailing captain, who says that if and when you see fire on a boat...don’t even bother putting it out, just emit s.o.s, wear your pfd, grab your essentials and jump overboard. I sure wouldn’t wish to test the validity of his saying, but it just gives you an idea how ruthless fire is...I know you know it, anyway.

[Carl]

Btw, we do not have squirrels! Possibly because the tallest tree in the islands is parsley!

Oh you don't know how lucky you are...I had a pair move in the day we moved into our last house. It took me awhile to figure out the best way to trap them and get them out...also found out a few mile ride was not far enough either. Actually it took me so long to figure it out I made those squirrels fat as hell baiting traps in the attic, didn't help that I got lazy and left a big jar of Peanut butter in the attic. That house was a pain to get up there, had to clear out a closet, finagle a ladder in, then hoist myself up and in a tiny access hatch. Any I left the jar up there and they ate through the side, sometime after that the sound of them running around went from a scamper to thump thump thump. I got finally got them evicted,,,but through the years I had about a half dozen. And raccoons...oh what a mess that was.

I have a friend, seasoned sailing captain, who says that if and when you see fire on a boat...don’t even bother putting it out, just emit s.o.s, wear your pfd, grab your essentials and jump overboard.

Before jumping overboard...access the situation. If too far gone or you have to run through flames to get a fire extinguisher, yes get going. But the right fire extinguisher, used properly and soon enough can do wonders. I think I mentioned my dad had a fire on his old boat years ago when trolling late night for Stripers, called for help, used fire extinguisher, but kept flaming up...about ready to jump and several of his buddies were at the boat jumping on with fire extinguishers, deck wash down hose they got the fire out long enough to find and fix the problem...towed him back in. Jumping overboard would have made for a tough night in the water back in the days of just Compass and Charts

[Yannis]

On the fire topic, my electrician told me yesterday, as we were discussing the eventuality of my catching fire due to my electrical magic, that very recently on a boat they were putting the fire out alright, but the cables were burning internally so a few moments later fire was bursting out of them in different locations...it took them days to put it out completely! The boat was wrecked as a result. Better let her go down, at least you’ll get your money back from the insurance, no?
Hold a PLB like the one we were discussing and go fishing, I mean scuba diving!

[Carl]

While I do not mind being in the water, I do not want to be out at sea in the water without a boat if I can help it.
In the water at night, no thanks.

If the boat was dangerous...yes, sure in the water I go.
I just think my chances are better in a boat over a raft.
In a raft over in the water.

Its about seeing and being seen
Staying drier and warmer
Not becoming bait...

[Tony Meola]

Electrical and gas fires are hard to put down but if you know what you are doing and catch it fairly quickly you can do it. We did it on a car with the gas overflowing from the Carb. I was hitting the topside with an extinguisher while another guy was on the ground hitting it from the bottom putting out the fire from the gas running down the engine.

Leaving the boat is the last resort. Remember, you are in the water, that is not your natural environment and unless you have a raft. Without a raft you have another set of issues to deal with.