Starter exciter input drawing >10A, normal?

[John A]

Originally Posted by jbrownson

Yeah, that was my guess too, but they replaced it when it was rebuilt though. It's theoretically possible the new one is faulty too, but...

That's what the first and second mechanics told me too. I used my cell phone to cancel a check to the second mechanic while I was being towed by Vessel Assist.

[gspeak]

I had the same problem on one of my 3gm30. Quick & inexpensive fix was to wire a relay in at the starter as previously mentioned.

[Jim Cate]

In my experience this problem is often caused (as others have suggested) by excessive voltage drop in the circuit from battery to start button switch to solenoid. In many boats the factory supplied wiring harness is not long enough so wires are spliced in... maybe not too well. There are often several multi pin connectors in the harness, each with the potential for a bad connection. Sometimes the start switch itself has a high resistance connection in it.

There are several ways of approaching the repair: find and replace the faulty bit, replace the whole circuit with better wire and connectors (if really needed in your installation) or keeping things as they are and add a relay near to the solenoid, again as others have suggested. The latter will surely work and is not expensive or complicated to set up, and is the way I chose to do it on my previous boat.

And FWIW, I always wire up a seperate starter button directly to the solenoid with short leads. This gives an easy way to start the engine if the solenoid should fail and is handy for starting up while working on the engine... no need to go out into the cockpit to reach the regular starter button.

Cheers,

Jim

[jbrownson]

I checked the ground wiring, and it all looks great visually.

I went to a couple of automative stores and they didn't have any in stock believe it or not, so I swung by West Marine to get some marine wire, some ends and saw this guy SIERRA 18-5816 Solenoid - Flat Bracket at West Marine

They call it a solenoid, but I've read that oftentimes solenoid and relay are used interchangeably and this looked like a relay I could use as described in the above answers.

The store was about to close and I didn't have a ton of time to research it on my smartphone. The package itself only listed what it was a replacement for and didn't give any specs on the unit itself, but it looks beefy enough to handle 30A so I bought it.

I tried to look up a spec sheet for the unit online when I got home, but didn't find one.

Looking at the device it looks pretty obvious how it's set up. The two smaller terminals look like the low current side and the two larger ones look like the high current side. afaik there usually isn't any polarity to it so I went ahead and wired up the low current side with one side going to ground and the other coming from the start button and sure enough when I press the button I hear a click and the two large terminals go from an infinite resistance to being connected just as I would expect based on my assumptions.

However... if I hook up the high current nodes between power and the low current input of the starter solenoid and press the button I hear the unit click, but the current doesn't flow between the high current nodes of the smaller solenoid. I tried reversing the connections on the high current side thinking there may be a diode in there for some reason and that didn't help either.

If I short the high current nodes of the small solenoid with a screwdriver the starter engages perfectly, so it seems like I've wired everything correctly, there isn't a ground fault, but the small solenoid isn't working as I expected it to.

Does anybody know where I can get more data on this part? Maybe I'm making a bad assumption about the pinout of it?

Here's an annotated photo of it installed: imgur: the simple image sharer

[btrayfors]

Jim Cate has it exactly right!

The problem is very likely to be excessive voltage drop to the solenoid, due to built-up resistance in the start-button circuit.

This was/is my problem for the past 15 years. Guess what? I simply wired in a start button with short leads directly to the start solenoid. Never a problem since.

You can't always find the voltage drop by measuring an inactive circuit. The amperage required to drive a multimeter is miniscule. But the solenoid requires a significant amount of amperage, and if there's a bad ground or excessive resistance in the circuit the solenoid will click but not make full contact.

On my boat, when the battery voltage is high or the battery charger is on, the cockpit start button will usually work OK, though sometimes requiring a couple of pushes. The other start button, with the short leads, works 100% of the time and has done so for 15 years. I put mine in the engine room behind a hinged door. It's also convenient for turning over the engine or starting it when changing oil, etc.

Bottom line: don't always assume that the problem is complex. Sometimes, it's just something very simple. Go for the simple solutions first :-)

Bill

[Nor'Sea 27]

Are you using your Yanmar wiring diagram as part of your current data?

[bill good]

"If I short the high current nodes of the small solenoid with a screwdriver the starter engages perfectly, so it seems like I've wired everything correctly, there isn't a ground fault, but the small solenoid isn't working as I expected it to."

You are missing the advise being offered. However we all learn by mistakes. The type of unit you have bought also has low resistance winding & will also draw as much current as the unit on the yanmar starter relay/solinoid!! You have taken the feed from the button AFTER the faulty plug & that won't help. If you used the general purpose type of relay recommended which has a high resistance winding with a LOW current to operate, it would have worked.

As stated this is a common fault with this loom that can be overcome by several approaches but all are aimed at removing that voltage loss over the circuit (which is the heavy wires) from the motor up thru the 30 amp fuse to the key & back to the starter relay/solinoid circuit.

Hopefully you next report will be that it is fixed!!

Bill

[Nor'Sea 27]

Too add to what Bill wants you to try

Consult the Yanmar wiring diagram. Note that the path is: red from battery (at B on the starter solenoid), then to fuse (in line holder), then to panel key, then white to start button (both back of Yanmar panel) , then white to starter solenoid (S at start solenoid. ) So there are 5 connection points that can go bad (if you have factory loom extension there are two more sets of connections.) Anyhow -- check them all. The likely failure modes include the factory inline fuse holder (30 amp) - an obvious candidate for corrosion because it is a moisture trap and the fuse is hidden in the holder. The rest are not hidden so corrosion is not as likely - more likely wire fatigue/fractures or loose fastener nuts.

Charles

[bill good]

ps even if you tighten the connections in the plug & socket the fault will reoccure over time. The simpliest would be remove the plugs & hardwire it.

[daddle]

Did I read it wrong? To me all the evidence points at a high resistance fault between the key switch and the "exciter" terminal of the solenoid. Corrosion, loose wires, etc.

1 - Shorting to the "exciter" terminal works every time.
2 - 6V measurement when keyswitch is used.

[Jim Cate]

Originally Posted by daddle

Did I read it wrong? To me all the evidence points at a high resistance fault between the key switch and the "exciter" terminal of the solenoid. Corrosion, loose wires, etc.

1 - Shorting to the "exciter" terminal works every time.
2 - 6V measurement when keyswitch is used.

Why yes Daddle, that is exactly what we have been saying... your "high resistance fault" is what is causing the excessive voltage drop that we have been suspecting.

Cheers

Jim

[jbrownson]

The key thing that made me want to use a relay after doing all I could to eliminate obvious wire problems is that I was seeing more than 10 amps in a line rated for no more than 6-10 amps. If there were additional resistance on the line from corrosion etc there would only be less current (correct me if I'm wrong here, just applying ohms law). The wire is simply undersized for the load. Maybe when it was brand new it would work due to conservative tolerances in the AWG current ratings or the like, but I don't want the system to be relying on that and I don't want that much current flowing through an undersized wire, especially one that long that goes through a bunch of turns next to other wires.

With the new relay the voltage drop on the starter button wire is muuuch less (which implies much less current, though I haven't replaced the fuses in my meter yet to verify this). The voltage is almost all dropped across the new relay which is great, and I hear it give a nice solid click, and w/o a load the high current ends seem to drop to ~0ohms just fine, which is why I'm baffled that with a load on them the connection doesn't seem to be made which has me really puzzled...

One thing I didn't try this morning that I'll try when I get home is to directly connect the low current input of the new solenoid to power to eliminate the possibility of a weak activation. If that starts it then I'll look more closely at the wires, but everything I've seen so far makes me think they're actually okay for reasonable currents.

The likely failure modes include the factory inline fuse holder (30 amp)

Hrm, I hadn't found that one. I'll take a look for it tonight too. TBH I didn't actually realize the wiring diagram for this would be in the engine manual. I looked in the boat manual and found some wiring diagrams, but they didn't include this. I'll definitely take a closer look at the engine manual too. Thanks.

Even if I find a bad connection in the wires somewhere I think I'm going to try to stick with the relay install if I can get it working. I just don't like that much current running through such a long undersized wire.

Thanks for all the responses!

[hellosailor]

The folks at Bendix (Corp) invented a starter engagement device which ran out of patent a long time ago. For a long time all of the engagement mechanisms were called "a bendix" the same way we say "kleenex" instead of "tissue" in the States.

AFAIK a solenoid is a coil with a bar running through the center. When power is applied the bar moves, sometimes to throw a switch, sometimes to throw a door lock or other machanism. As opposed to a relay, where a coil only pulls down some contact arm(s) that are sitting on the end of it.

A "bendix" should be a solenoid, to physically throw the motor in/out against the flywheel, but sometimes there's also a relay which allows direct battery voltage to be applied to the starter motor instead of the lower power coming from an ignition key circuit.

So...for repairing things the differences would be important but from the black box point of view, they're all "thingies" that move stuff around in the starter assembly.

(Thingie being a technical term as used in the Beatles movie "Help!".)

If it is a solenoid, sometimes they get jammed up from congealed grease and crud and fail to fully engage and a simple cleaning with solvent spray is all they need to work again.

If it is a relay the relay goes "click" the contact arms either are or aren't making contact, and "click" means they made contact. But every contact and break involves an electrical arc that eats away the relay points, so eventually they wear out. Onceuponatime, we used a "relay point file" and simply filed them down to shiny and new again. And the best relays were sealed, with mercury wetting the contacts to prevent arcing.

These days...starter repair is usually a matter of checking the wires for power, and then pulling the starter out for R&R. No matter what's in the box.

But around here, if I took a starter into a shop and said there was a problem with the "exciter", they'd do their best to rob me blind, since I'd just shown I had no idea whether I had the starter or the alternator in hand. Just saying, sometimes the details count.

[daddle]

Oops. I missed the second page. I see you all are "on it" now after some initial odd conclusions. Sorry for the interruption.

[jbrownson]

Okay guys I think I got it solved. The relay folks were absolutely right.

I did some more research and I read in the iphomeport forum that Yanmar has actually issued a service notice that a booster relay should be installed in certain circumstances where the wiring is insufficient, and folks have been told by yanmar technicians that this can be a problem (all second hand of course, I couldn't find any yanmar notices, not sure where I'd look). I checked the manual for the current model of my yanmar and it shows a booster relay wired in just as mine is now.

That said I did re-double check the wires and connections, specifically locating the fuse. The fuse connection did look a bit loose (though the multimeter indicated things were fine), but securing it didn't help the situation (though it might prevent a future one).

So I went back to trying to install the relay. As I mentioned the solenoid/relay I bought doesn't seem to have any spec sheet anywhere, so I had to guess a bit on the pinout. I realized that of course the input to the relay is polarized because if the magnetic field is reversed it's going to push the core away from the contact which would still make a click as I was hearing, but wouldn't make a contact on the high current side. I swapped the inputs and hasn't failed to start since.

Thanks for all the replies and help! I learned a lot doing this.