Yanmar charging light faintly glowing, 13.8V across battery

I've had recurring alternator issues ever since I installed a new alternator and external regulator 4 years ago. In all cases I've found that the "professionally factory installed" crimps and terminals have all failed. With 18 connections and over half a dozen at the back of the alternator (not including the ones I made myself which haven't failed - yet?:)) I have replaced/repaired all of the factory ones.

Given this discussion, it appears that there are step-by-step issues for the OP to address and perform:

1. Take off the connections, clean them up and see if that's the trick - it could well be

2. Then go further from there by addressing the guts of the alternator either by himself or at a shop.

Many of us have found that the biggest glitch in every electrical system is the connections, and always the first and easiest to check.
 
Stu Jackson said:
Many of us have found that the biggest glitch in every electrical system is the connections, and always the first and easiest to check.
Click to expand...

+1

On the Balmar web site you can download their alternator manuals.
At the end of the manual is some information about alternator testing.
i.e. http://www.balmar.net/PDF/12V Alternator Manual w-90series drawing.pdf

Personally if it is a connection than I would look for the one that connects the alt lamp to the alternator as that is the one that is not reaching the battery voltage. (As this voltage nears the battery voltage the lamp will go off. You could just measure this voltage directly off the back of the alternator but I suspect it will be one of those you can't get to unless you take the thing off.) As others have said it could be a host of things from a loose pulley wheel, a worn belt, or brushes or the brushes themselves have worn through the contacts on the stator (or whatever it's called.)
On an alternator that's 12 years old I wouldn't spend any money getting the alternator itself fixed as it may soon be in need of new bearings etc anyway. Just don't think you have to buy a Yanmar alternator to do the job. They are silly prices.
 
lenseman said:
Glowing faintly will always be a bad earth, never a brush.

A brush fault will always be lamp on or lamp off never glowing.

What causes people to think it is caused by the brushes is the fact that to inspect the brushes, they remove the battery live terminal (or earth terminal) remove the alternator. The brushes are then inspected, repaired or changed and everything is returned to the engine and the battery terminals are then reconnected.

Everything is good, no glowing lamp and it is therefore assumed that the brushes we at fault when in fact disturbing and reconnecting battery terminals or alternator body has in fact effected a cure. :)
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Wrong!
Stu
 
VicS said:
Why?

Explain your reasons for saying it's wrong.
Click to expand...
Vic
happy new year, am sure you have noticed the new years resolution?

"Glowing faintly will always be a bad earth, never a brush"

Thats whats wrong. I dont have to explain it to you, youve already posted similar ideas to mine so I know you understand how they work.
Ive added my years of experience fixing the things. My real time experience tells me, light slightly glowing then going out when revved, then it steadily gets worse till the slightly glowing light wont go out when revved is a steady deterioration of the brushes. No input means no output. Simple really!
Stu
 
skipper_stu said:
Vic
happy new year, am sure you have noticed the new years resolution?

"Glowing faintly will always be a bad earth, never a brush"

Thats whats wrong. I dont have to explain it to you, youve already posted similar ideas to mine so I know you understand how they work.
Ive added my years of experience fixing the things. My real time experience tells me, light slightly glowing then going out when revved, then it steadily gets worse till the slightly glowing light wont go out when revved is a steady deterioration of the brushes. No input means no output. Simple really!
Stu
Click to expand...

I think Vic knew this as Vic and I were getting there through my questioning of:

Quote:
Originally Posted by VicS
There would be a poor connection to the field coil, whichever brush it was.
Originally posted by Talulah
Understood but would there be any physical indications that this may be happening without dismantling the alternator?
etc
 
Talulah said:
I think Vic knew this as Vic and I were getting there through my questioning of:

Quote:
Originally Posted by VicS
There would be a poor connection to the field coil, whichever brush it was.
Originally posted by Talulah
Understood but would there be any physical indications that this may be happening without dismantling the alternator?
etc
Click to expand...
Vic asked me nicely to explain, I answered in the same vein.
Stu
 
Talulah said:
I was just trying to be subtle. Instead of "Wrong".
Click to expand...
He was wrong

"Glowing faintly will always be a bad earth, never a brush.

A brush fault will always be lamp on or lamp off never glowing"

I know that, you know that, Vic knows that, a few others know that, so whats wrong with saying that?

Stu
 
Been out of intarwebs contact today...

The lamp glows faintly at all engine revs. I'm pretty certain that it's charging poorly (or the batteries are knackered) as it didn't turn the engine over that quickly on Sunday.

Sunday was the first time I've visited the boat in 2 months -- busy at work, snow, Christmas, etc. I don't leave her plugged in as she's switched off, pretty dry and as it's been freezing so damp's not an issue.

The 2 batteries are fairly old, but as they did start the engine, they're holding a charge, especially after 2 freezing months. The charging light has been noticeable for a few months (I keep putting it off!). I'm not sure if the lamp comes on when the key's turned as the panel's inside the boat just under the companionway step and I tend to be outside when I crank it as the screaming pressure alarm isn't a place to be when starting.

So, to-do...

I'll check all the terminals, reseating them. I'll also check the connections to the 2-way switch.

I'll remove the alternator after first disconnecting the batteries -- thanks for that tip! I'll check the diode block (will see how when I open it). I'll also check the brushes, clean it out and see if the bearings are OK.

I've had a look on the intarwebs and found
http://www.startermotor-alternator-store.co.uk/marine-alternator-21-c.asp
and
http://www.trickettmarineproducts.co.uk/yanmar-alternators.html
which seems to be not too unreasonable.

So it looks like I know what I'm doing next weekend:-)

Thanks so much for the advice.
 
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
 
Last edited:
I've had a look on the intarwebs and found
http://www.startermotor-alternator-s...nator-21-c.asp
and
http://www.trickettmarineproducts.co...ternators.html
which seems to be not too unreasonable
Click to expand...
.

Good heavens!

Your local automobile electrician should be able to fix it up for a fraction of those prices.

It absolutely impossible to diagnose the problem via a web forum.

Based on what has been said check the external connections and inspect the brushes.
Then get the alternator tested.
I think thats the most sensible plan.
 
keeping on the subject of alternators, I have a problem - although seeming quick to resolve.

When I start my engine all seems fine, but if I have not given it any revs (i.e. left the engine ticking over in idle), my battery charging light comes on (i.e. the warning light to say the batteries are NOT charging).

This I have found is quickly 'fixed' by giving the engine some revs, say just above tickover.

Is this a problem, or is this normal?
 
In view of all the suggestion and comments made it would be nice if the OP would kindly post the results of the fault, one can learn a lot from the findings. Thanks.
 
Great exchange of info.....

pampas said:
In view of all the suggestion and comments made it would be nice if the OP would kindly post the results of the fault, one can learn a lot from the findings. Thanks.
Click to expand...

This whole post has been one of the best I have ever read here. Shorn of social chat it should be published in PBO as is - worth more than hours sitting in electronics classrooms.

Thanks guys!

PWG
 
PeterGibbs said:
This whole post has been one of the best I have ever read here. Shorn of social chat it should be published in PBO as is - worth more than hours sitting in electronics classrooms.

Thanks guys!

PWG
Click to expand...

It will be useful once we know what the caused the problems!
 
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