YM1110D Won't Charge

[rScotty]

I got up this morning and re-read what I had written as reply #10. It was kinda confusing so I saw I could edit it and just did so.
It's a lot better now.
My apologies to anyone trying to make sense of the original. That will teach me to try to type up something while doing something else at the same time.
rScotty.

 

[OhioBruce]

After dropping it and breaking off a chunk when trying to bend it back, I cleaned off some grime and desoldered it. Then I labeled each diode like this:



Here is what it looks like under the plates:




Then I took the following readings:

Diode 1 - Negative on the plate, positive on the diode wire = .605 ohms. Positive on the plate and negative on the diode wire = no continuity.
Diode 2 - Negative on the plate, positive on the diode wire = .560 ohms. Positive on the plate and negative on the diode wire = no continuity.
Diode 3 - Positive on the plate, negative on the diode wire = .613 ohms. Negative on the plate and positive on the diode wire = no continuity.
Diode 4 - Positive on the plate, negative on the diode wire = .611 ohms. Negative on the plate and positive on the diode wire = no continuity.

I also verified there was continuity between each diode housing and the mounting plates.


Diode 2 is off from the others, but doesn't seem to be that big of a difference? So, maybe it is the voltage regulator?

 

[CoyPatton]

After dropping it and breaking off a chunk when trying to bend it back, I cleaned off some grime and desoldered it. Then I labeled each diode like this:



Here is what it looks like under the plates:




Then I took the following readings:

Diode 1 - Negative on the plate, positive on the diode wire = .605 ohms. Positive on the plate and negative on the diode wire = no continuity.
Diode 2 - Negative on the plate, positive on the diode wire = .560 ohms. Positive on the plate and negative on the diode wire = no continuity.
Diode 3 - Positive on the plate, negative on the diode wire = .613 ohms. Negative on the plate and positive on the diode wire = no continuity.
Diode 4 - Positive on the plate, negative on the diode wire = .611 ohms. Negative on the plate and positive on the diode wire = no continuity.

I also verified there was continuity between each diode housing and the mounting plates.


Diode 2 is off from the others, but doesn't seem to be that big of a difference? So, maybe it is the voltage regulator?

Any time checking continuity, I prefer clean contact points. Meaning you would probably get slightly less resistance if the plate were clean at least where you placed the lead.
But regardless your readings are correct for 1 way diodes.
Also I have no ideal how the diode is mounted to the plate so some of the resistance could be from this as well.

I have no ideal on where the resistance should ohm at for those diodes, but issues with the regulator mounted on the firewall would not surprise me at all.

 

[rScotty]

Congratulations! You just tested all the diodes and they came out good. The one that tested differently is suspect, but it's within 10%, so I'm going to call it good. In fact, it is looking like your alternator is good. Time to clean and reassemble. Then of course we wil then test it one more time before going on to the voltage regulator.

Going back to message #9, I assume that with the alligator leads clipped on like you show, that the readings you got were AC voltages.. true? And that told us the internal alternator coils and magnets are good. Now that we don't have the diodes in the circuit might as well now double check that neither of the coil wires has continuity to the case.

The photo in message #9 also shows the output wires from the alternator - looks like a yellow wire and a red wire with the red wire in a black sleeve.... Hmm... I wonder why the red wire is sleeved? I can't quite see where it comes from, but isn't it coming from a tab under the phillips screw? That would mean it was common frame ground so why sleeve it? It's the other one - the yellow wire - that I would expect to be sleeved.
Hmm....looking closer, why is there a butt connector on the red wire? Has someone been there before?
Hey! is that abrasion that I see on the yellow wire? Hard to make it out, but is there any chance that wire insulation is worn away and the yellow wire touching some part of the motor or frame? Surely not...although that would explain all.

So if the yellow wire isn't abraded and touching, solder all back up and then test the AC output like you did before. No point to go up to 20 volts. Just check that it is the about the same. And then hook your multimeter to the other end of those yellow and red output wires. This time when you rotate the alternator you will get about 3/4 of the voltage but it will be DC. Or at least it should be DC if the rectifier diodes are doing their job. Actually, what you will get is a pulsating DC, so depending on the sophistication of the multimeter and how fast you spin it the meter may try to tell you it is still looking at AC. Anyway, see what you get.

If you get about 3/4 of the voltage from the red and yellow wires and it is DC when spun fairly fast, then we have a good alternator and it can be put back onto the motor. The next step is the voltage regulator, but depending on how yours is wired, there is a chance that the ignition switch in involved.

With the alternator back on the engine, it is time to check the continuity on the ignition switch first, and then see what kind of voltage regulator that it has. Yanmar used several different VRs. And although we can fix them all, it is rarely worth the effort.

We check the ignition switch first because sometimes the alternator output runs through the ignition switch and then to the voltage regulator. You need to trace the wires to find out because Yanmar did it both ways. And because the corrosion on the back side of the alternator plates make us suspicious that the inside of the ignition switch may be similar. The switch can be taken apart and the contacts cleaned, but it is picky work and there are little springs in there that rust, too.....not to discourage you from trying.

And the voltage regulator is encapsolated in epoxy.
In fact, we may end up just ordering one or both from Hoye.

But first lets make sure the alternator is good. Put it back together, check for abrasion of the yellow wire, and give the AC & DC spin tests. If good, back on the engine it goes.
luck,
rScotty



The

 

[OhioBruce]

Coy - I filed a small spot on the plates and tops of the diode wires to get a fresh contact point. I think they are pressed in. I can't see any solder.


rScotty -
Message#9 was AC voltage.
Neither coil wire has continuity to the case.
Yellow wire is not abraded.
It does look like it's been worked on before. The phillips screw that holds down the red wire has a buggered head.
Checked AC output with nothing connected to the wires and I'm getting 5 volts just spinning by hand the same as before.

Heading out to put it back together.

 

[rScotty]

Coy - I filed a small spot on the plates and tops of the diode wires to get a fresh contact point. I think they are pressed in. I can't see any solder.


rScotty -
Message#9 was AC voltage.
Neither coil wire has continuity to the case.
Yellow wire is not abraded.
It does look like it's been worked on before. The phillips screw that holds down the red wire has a buggered head.
Checked AC output with nothing connected to the wires and I'm getting 5 volts just spinning by hand the same as before.

Heading out to put it back together.

OK. That's all good. What did you get from the two output wires (yellow & red) when you spun the alternator? Anything?

 

[OhioBruce]

I put everything back together and made sure I had fresh metal at all contact points. I also put some shrink wrap on that yellow wire to be sure it wasn't grounding out.

Set my multimeter to DC and clipped on the alligator leads. Gave it a spin and had about 3 volts. Pushed it against the wire brush and it quickly climbed to 12.7 volts DC. Woo Hoo!

So, given that I tested it with the same multimeter while the tractor was running and got nothing, I'm wondering if it had some corrosion or short somewhere? That screw that held the red wire was barely finger tight when I took it apart.

Now to put it back on the tractor and see what happens. First I need to get a belt - the old one is shot.

Thanks!

 

[rScotty]

I put everything back together and made sure I had fresh metal at all contact points. I also put some shrink wrap on that yellow wire to be sure it wasn't grounding out.

Set my multimeter to DC and clipped on the alligator leads. Gave it a spin and had about 3 volts. Pushed it against the wire brush and it quickly climbed to 12.7 volts DC. Woo Hoo!

So, given that I tested it with the same multimeter while the tractor was running and got nothing, I'm wondering if it had some corrosion or short somewhere? That screw that held the red wire was barely finger tight when I took it apart.

Now to put it back on the tractor and see what happens. First I need to get a belt - the old one is shot.

Thanks!

Maybe we got lucky and all it needed was cleaning. That's not usually the case with alternators, but then they aren't usually that corroded either.
A little bit of electrical current jumping across the micro-space between two dissimilar metals is as good as battery acid for promoting corrosion.

Cleaning was often the answer with old "DC" generators - the kind with brushes and commutators. But there is was usually carbon from the brushes everywhere. There was even a special tool used to clean out the slots in the commutator.

I always figure if I don't know what I'm doing, then cleaning and reassembling can't hurt & I might learn something.
And today as in yesteryear the key to making any carburetted gasoline engine that has set for awhile run right again is to simply take the carb apart, clean all the orfices, needle and seat, ....and reassemble.

We did sort of take the slow, craftsmanlike, step-by-step mechanical method, didn't we?
Good on us so far,
rScotty

 

[OhioBruce]

Yep, I've enjoyed taking this step-by-step and learning a little about alternators. I always fix anything I'm able to and like to put new skills in my toolkit. I appreciate your patient guidance.

You're right about cleaning a carb. I learned the hard way that you can't get by with just cleaning the needle valve and main jet.

I'll get a belt tomorrow, install it, and report back.

Thanks!
Bruce

 

[OhioBruce]

I got a belt, installed everything, cranked it up, and got this:







This was at 3/4 throttle. At idle it puts out 13 volts. Once I throttle up a little it climbs back up to 14 volts.


We did it, rScotty! :thumbsup: :thumbsup: :thumbsup:

Not only did I save a ton of money, I learned something along the way.

Thank you very much for helping me!