Yanmar charging light faintly glowing, 13.8V across battery

[GlennG]

Update - alternator is OK

I went up to the boat over the weekend, tweaked & twiddled and removed the alternator. I took it to an alternator specialist who stripped it down and found everything was fine. He put it on his test rig and it passed.

So, both good news and bad news. Good that it's not the alternator. Bad news in that it's got to be something else.

Reminder: engine is Yanmar 2GM20 with a 55 amp Hitachi alternator.

The prime suspects are now the two connector blocks from the engine to the loom. That and the engine earth. Annoyingly the two connector blocks are hard to get at; typical boat in that you can see them or touch them with one hand, but not all three. To do that I'll have to climb into the locker and use the inspection hatch -- I knew there was a reason for going on this New Year diet

I'll properly note down the voltages this time - I was so hoping that the alternator would be the root problem I didn't write down the measurements.

Back up to the boat on Saturday...

 

[lenseman]

. . . . Good that it's not the alternator. Bad news in that it's got to be something else. . . . .

Now re-read thread 14 and take a multi meter with you on Saturday.

You will have to check EVERY junction and joint and at least one will give a voltage higher than zero.

If you have a crew-member/partner to help you, you could start the engine and run it a 2,000 rpm and whilst your crew member very carefully watches the ignition light, you go to every single joint/junction in the heavy current side of the alternator and HARD WEDGE a small screwdiver point down between each lead where it changes from a lead to a bonding screw etc and repeat this for all connections. Long (3") Obo nails are good for this quick check as they have a very sharp steel point.

Your crew member should be able to see when you have found the junction using this method as the ignition light will go out. Otherwise you will have to start the engine and run at 2,000rpm and use a multi-meter and look for a voltage that should not be there.

 

[VicS]

As lenseman says check connections for volts drops that should not be there.

However. You do not have to start by doing every joint singly.
Check along whole sections encompassing several connections at a time. No volts over a whole section = no problem. When you find section with a volts reading then is the time to break it down and start checking individual connections.

Personally I don't think the problem will lie with joints that carry starter motor loads because that would lead to sluggish cranking.
I could be wrong of course.

At least you know the alternator is in good health and you wont have to worry about that for some time to come.

 

[Bosun Higgs]

To the OP. Ignore all this technical willie waving . Just check and remake as necessary all the electrical connections, check the brushes, and replace the battery if its dodgy anyway.

If then the battery is being properly charged ( ie mostly at 14 to 15 v before dropping back to 13.4 or thereabouts) and the little light is still glowing you have the choice of either ignoring things or coming back here for more of the same willie waving

 

[GlennG]

Would the alternator -ve be 'earthed' through the starter motor's -ve lead? (Not looked due to awkward access - need to clear out the locker & climb in to get access to that side of the engine).

The engine does crank OK, although it seems a bit slower than normal which I've put down to it being cold (or my imagination). If it's cranking OK, then the connection to/from the battery & starter should be OK.

I really appreciate the very helpful comments

 

[savageseadog]

Would the alternator -ve be 'earthed' through the starter motor's -ve lead? (Not looked due to awkward access - need to clear out the locker & climb in to get access to that side of the engine).

Yes. The engine "earth" or negative lead is very important

 

[Graham_Wright]

Belt tension? Classic on a car.

 

[Heckler]

To the OP. Ignore all this technical willie waving . Just check and remake as necessary all the electrical connections, check the brushes, and replace the battery if its dodgy anyway.

If then the battery is being properly charged ( ie mostly at 14 to 15 v before dropping back to 13.4 or thereabouts) and the little light is still glowing you have the choice of either ignoring things or coming back here for more of the same willie waving

Pissin contest is the correct term!
Will be interesting to see if the alternator now works correctly when he puts it back on.
Stu

 

[VicS]

Willy waving or not, pissing contest or not, any other vulgarities or not.

A bad joint anywhere between alternator and battery, positive or negative, could be the cause of poor charging and it may be more than one.
Just breaking, cleaning and remaking all the joints may find and cure it but if its a bad crimp joint it wont! Systematic testing will find it no matter where it is.

If a bad joint is causing the warning light to glow then there are a limited number of places that can be the cause. Studying the wiring diagram will help to identify those. They can then be checked out.

It will indeed be interesting to see if all is returned to normal when the alternator is refitted. If it is then the connections to the alternator or the battery or the alternator earthing were at fault.

There are two approaches

The scientific way: ... systematically test .. identify the problem ... fix it.

The engineering way: ... tear it all apart .... whack anything that looks suspect with a big hammer .. put it all back together ... hope and pray that it will then work.

I am a scientist ...... but I spent most of my working life in a heavy engineering environment.

 

[vyv_cox]

Yes. The engine "earth" or negative lead is very important

Sometimes, most often on older cars, the earth lead is not insulated. Over time it can corrode away. I recall having some starting problems and opened the bonnet in the dark while someone else operated the starter switch. The cable was glowing red hot!

 

[Heckler]

Willy waving or not, pissing contest or not, any other vulgarities or not.

A bad joint anywhere between alternator and battery, positive or negative, could be the cause of poor charging and it may be more than one.
Just breaking, cleaning and remaking all the joints may find and cure it but if its a bad crimp joint it wont! Systematic testing will find it no matter where it is.

If a bad joint is causing the warning light to glow then there are a limited number of places that can be the cause. Studying the wiring diagram will help to identify those. They can then be checked out.

It will indeed be interesting to see if all is returned to normal when the alternator is refitted. If it is then the connections to the alternator or the battery or the alternator earthing were at fault.

There are two approaches

The scientific way: ... systematically test .. identify the problem ... fix it.

The engineering way: ... tear it all apart .... whack anything that looks suspect with a big hammer .. put it all back together ... hope and pray that it will then work.

I am a scientist ...... but I spent most of my working life in a heavy engineering environment.

The engineering way is the same as the scientific way, BUT an engineer has had hands on experience and can fall back on that. So in this case the engineer knows the prob is caused by there not being enough voltage coming from the alternator to balance the voltage from the batteries. He thinks about the way to find out why it isnt happening. He knows from his vast hands on experiences that it is usually the brushes in the alternator that are not making good contact with the commutator and failing to excite the windings enough.
He also knows that it can be a bad connection, but his vast hands on experience says it is less likely.
He then uses his vast hands on knowledge to easily check whether the brushes in the alternator are sticking, worn, or that the commutator is dirty. When he is satisfied that all is well with the alternator, he can then recheck whether it is charging correctly. If it isnt, he then goes on to check connections etc. He does this last because his hard won knowledge tells him which is the most likely problem.
A scientist however, not having vast hands on experience in maintaining such things does quite a bit of toothsucking, willy waving, pi ssin contesting and sits on the fence. He cant do otherwise because he doesnt have previous experiences to draw on.
Eventually they both get to the same position, the problem is solved, however the engineer usually gets there quicker!
Stu
PS dont forget, I made a NY resolution!

 

[Heckler]

Yes. The engine "earth" or negative lead is very important

There is no engine earth on my boat, the MD22 is electrically isolated/insulated
Stu

 

[savageseadog]

There is no engine earth on my boat, the MD22 is electrically isolated/insulated
Stu

Yes but we're talking about a Yanmar 2GM20 with conventional alternator and starter, as far as I know, which have an engine connected earth or negative return for both components.

 

[steve28]

helpful tip for checking hitachi brushes is the wear limit is the hitachi symbol on the side of the carbon brush.

Also check the wiring harness connection at the back right hand side of the engine as the terminals corrode in the plug / socket, two of these wires are to do with the warning light.

Steve

Check the inline fuse 12 volt feed to the starting panel, located in the same area as the inline connectors. These also cause problems with corrosion.

Steve

 

[VicS]

Check the inline fuse 12 volt feed to the starting panel, located in the same area as the inline connectors. These also cause problems with corrosion.

Steve

Yes something well worth checking but looking at the wiring diagram I can't see that it will cause the problems in question unless some additional electrical load had been added to the circuits it supplies ... then it could.

If the problem persists when the alternator is reinstated I'd start by checking the connections on its main + ve output wiring.

I cannot see how any poor earthing connections will cause the charge warning light to glow.

Typical Yanmar wiring diagram

 

[GlennG]

Update - alternator re-fitted, still glowing

Didn't have much time on Saturday, so did the following:

* Prised one of the two engine connectors apart and re-seated it (there's two connector blocks, one with lots of cables, one with three thicker cables). Couldn't get the other connector to part. (reminder: engine's a Yanmar 2GM20)

* Replaced the alternator, tightened belt, etc.

* Measured the open-circuit, quiescent voltage of the batteries: 12.48V & 12.47V.

* Reconnected batteries. Noticed slight spark when re-connecting the starter battery (must be some electronics starting - alternator field? Both the fridge & heater are not connected through the switch panel).

* Switched battery master switch to both.

* Started engine. Charging light is bright on when engine not running (e.g. alarm blaring). Charging light is dimly glowing when engine running at 2000RPM.

* Measured battery voltages when engine running: 14.23V (switch on both), 14.32V (switch on either house or starter). BTW when master battery switch on one battery, the other then measured around 13V, but falling -- I guess this is because it's just got a charge.

* With engine running at 2000RPM and master switch on both, I connected the meter to the +ve connection of the battery and measured the voltage from the alternator output. This was 0.08V. Seems to me that a 80mV drop across the loom is fine.

* I can't measure the alternator earth to battery earth as I can't see the connection with the alternator fitted (call me a woos, but I'm not keen on poking the meter prod around the back of the alternator by feel when the engine's running!).

* Then it was too dark to continue...

I'm going back to the boat later to continue. I'm keen on running a wire from the alternator -ve to measure the drop from it to the battery -ve.

I'm also going to connect the boat to the shore power and charge the batteries using the full charger. I'll also re-read all your excellent advice, especially regarding the instrument panel.


Thanks

 

[sailinglegend420]

Why don't you all stop trying to score points?

Let the poor OP try what has been suggested so far.

I had EXACTLY his symptons and it was an internal fault where the output wires from two diodes out of 6 were not crimped properly and had finally burnt and blackened the interior. When I repaired it our 100 amp alternator was charging at up to 100 amps for the first time in 6 years.

Taking the alternator to bits is easy - getting it back together is more difficult. Search online depending or your model.

 

[VicS]

Why don't you all stop trying to score points?

Let the poor OP try what has been suggested so far.

I had EXACTLY his symptons and it was an internal fault where the output wires from two diodes out of 6 were not crimped properly and had finally burnt and blackened the interior. When I repaired it our 100 amp alternator was charging at up to 100 amps for the first time in 6 years.

Taking the alternator to bits is easy - getting it back together is more difficult. Search online depending or your model.

At the risk of being accused of "scoring points"
It should be noted that OP has had the alternator tested!

 

[VicS]

Didn't have much time on Saturday, so did the following:

* Prised one of the two engine connectors apart and re-seated it (there's two connector blocks, one with lots of cables, one with three thicker cables). Couldn't get the other connector to part. (reminder: engine's a Yanmar 2GM20)

* Replaced the alternator, tightened belt, etc.

* Measured the open-circuit, quiescent voltage of the batteries: 12.48V & 12.47V.

batteries are not flat by any means but somewhat short of being fully charged

* Reconnected batteries. Noticed slight spark when re-connecting the starter battery (must be some electronics starting - alternator field? Both the fridge & heater are not connected through the switch panel).

With nothing switched on there should be no spark. The field is only energised when the keyswitch is ON. Something there to investigate maybe.


* Switched battery master switch to both.

* Started engine. Charging light is bright on when engine not running (e.g. alarm blaring). Charging light is dimly glowing when engine running at 2000RPM.

* Measured battery voltages when engine running: 14.23V (switch on both), 14.32V (switch on either house or starter). BTW when master battery switch on one battery, the other then measured around 13V, but falling -- I guess this is because it's just got a charge.

14.2 - 14.3 sounds good IIRC it was much lower originally. It more or less confirms that all is well with the alternator and that it is charging the batteries OK
Yes once switched out the battery volts will fall quite quickly. How quickly depends on the state of charge and the overall condition


* With engine running at 2000RPM and master switch on both, I connected the meter to the +ve connection of the battery and measured the voltage from the alternator output. This was 0.08V. Seems to me that a 80mV drop across the loom is fine.

80mV is not enough to make the warning light glow. (I tried a couple of 12 volt bulbs on a 1.5 volt battery Even that's not enough to make them glow more than very dull red.
Is 80mV significant? If the alternator was charging at a good few amps probably not. If the battery had by this time been fully charged and the current dropped right back, or if cranking is sluggish, then perhaps worth a bit more investigation.


* I can't measure the alternator earth to battery earth as I can't see the connection with the alternator fitted (call me a woos, but I'm not keen on poking the meter prod around the back of the alternator by feel when the engine's running!).

No I dont like doing that. Quite apart from the risk of of shorting something the drive belt is a hazard too far for my liking. Maybe measure from the alternator casing, assuming its not insulated


* Then it was too dark to continue...

I'm going back to the boat later to continue. I'm keen on running a wire from the alternator -ve to measure the drop from it to the battery -ve.



I'm also going to connect the boat to the shore power and charge the batteries using the full charger. I'll also re-read all your excellent advice, especially regarding the instrument panel.

Nothing much more to contribute I am afraid.
I think having had the alternator tested and confirmed that it is charging OK I might leave it at that pending some flash of inspiration.

 

[GlennG]

Update - more investigations!

OK, the story so far... Removed the alternator and had this tested at a specialist alternator workshop. They said it was fine, worked fine on their test rig and the brushes were fine. Amazingly, no charge for testing it!

Re-fitted it yesterday, light still faintly glowing.

Today's work...

Disconnected, jiggled, re-connected all connectors including the 2 engine connectors (sods to get at & disconnect); 1 engine inline fuse (what a place to hide it! - I opened it and moved it around to re-seat it); 1 connectors from the loom to the in the control panel; two or three other connectors in the control panel.

Removed the alternator, added a small wire from the -ve connection to be able to measure the ground when the engine's running.

* Measurement from the alternator -ve to the battery ground is 0.12V, i.e. 120mV.

* Measurement from alternator -ve to alternator +ve is 14.31V.

Light is still stubbornly on (glowing dimly when the engine's running - glows brightly when the engine's not running). Really regrett not measuring the voltage across the light!

I've connected the boat to the mains electricity and left the charger on; the idea being to really fill the batteries with lots of electrons. It's a Stirling smart 4 stage charger (had to also shell out the £68 for the electricity meter which I've been putting off!)

....

So it now looks as if I've been around the whole course for the first time. One of the main things that I'm concerned about is that I've no way of knowing the true state of the batteries; are they being charged, if so by how much. So I'm fairly convinced that I'm going to invest in a battery monitor, if nothing else to show how many amps are flowing around the system. Does make sense when sailing longer distances or when on a mooring.

I like the Nasa compact battery monitor, but this has the drawback of monitoring only one battery. Would like a battery monitor to monitor the state of both especially as they spend so much time connected together (the charging switch on Both). Any recommendations for alternatives?