Weird charging problem. Or maybe not?

[DoubleEnder]

When the engine is ticking over the red charging warning light just glimmers. Barely visible. But, when I increase revs the light comes on bright! No audible alarm, however.
The belt is tight, and new. The pulley wheels are clean. I really don't think it is slipping.
I am not running any electrical equipment other than the engine panel itself.
I didnt have a multi meter on board today when I went down just to check lines and run the motor a bit, so I guess the first thing is to check current and volatge at the aletrnator terminals. But, any ideas?

 

[S04]

With the ignition on but before starting the engine is the charging lamp fully lit with the alarm sounding?

 

[PaulRainbow]

When the engine is ticking over the red charging warning light just glimmers. Barely visible. But, when I increase revs the light comes on bright! No audible alarm, however.
The belt is tight, and new. The pulley wheels are clean. I really don't think it is slipping.
I am not running any electrical equipment other than the engine panel itself.
I didnt have a multi meter on board today when I went down just to check lines and run the motor a bit, so I guess the first thing is to check current and volatge at the aletrnator terminals. But, any ideas?

Take the alternator off and get an auto electrics company that does starters and alternators to check it, it's almost certainly faulty.

 

[PabloPicasso]

Circuit test meter thingys arrrr cheap these days.

I have one aboard, and another at home.
Buy one and keep it on board

£8.65 for a digital.multi.meter on amazon. If thats too much you could probably get them cheaper elsewhere.

 

[William_H]

I can't imagine how it starts off dim then gets bright with engine RPM. However light remaining on indicates alternator is not able to provide it's own excitation voltage (to rotating field coil). As always check all connections for intgrity but as suggested may need a specialist to run it up on a test bench. ol'will

 

[Boater Sam]

Field diode shorted in the alternator.

 

[DoubleEnder]

With the ignition on but before starting the engine is the charging lamp fully lit with the alarm sounding?

Yes it is.

It’s a new problem, only noticed yesterday. I will measure the volts and amps but probably best just to take it to a specialist I guess. The boat is on the Hamble. I live near Oxford. Any recommendations?

Thank you everyone

 

[DoubleEnder]

Circuit test meter thingys arrrr cheap these days.

I have one aboard, and another at home.
Buy one and keep it on board

£8.65 for a digital.multi.meter on amazon. If thats too much you could probably get them cheaper elsewhere.

Yes. I take a lot of gear off the boat in the winter. Wooden boat, so I empty lockers, leave doors open, boards up, all that sort of thing. My goal is to maximise ventilation

 

[Alex_Blackwood]

Take the alternator off and get an auto electrics company that does starters and alternators to check it, it's almost certainly faulty.

Totally agree with Paul, probably duff diode or such, but can I suggest that you check all your connections first? Perhaps disconnect and redo starting at alternator and work through, give it a test run at each stage to see if you can identify which is at fault.

 

[Shaz77]

When the engine is ticking over the red charging warning light just glimmers. Barely visible. But, when I increase revs the light comes on bright! No audible alarm, however.
The belt is tight, and new. The pulley wheels are clean. I really don't think it is slipping.
I am not running any electrical equipment other than the engine panel itself.
I didnt have a multi meter on board today when I went down just to check lines and run the motor a bit, so I guess the first thing is to check current and volatge at the aletrnator terminals. But, any ideas?

Depending how big it is of course used alternators on ebay start at about £30 and if money is no problem get a replacement. Usually once they start messing around that's it. Something shorted or burnt out inside due to lack of use and a salt laden environment.

 

[billskip]

It may just be the carbon brushes (if fitted)

 

[PaulRainbow]

It may just be the carbon brushes (if fitted)

That's the most likely thing, or the regulator, which usually includes the brushes.

 

[PaulRainbow]

Yes it is.

It’s a new problem, only noticed yesterday. I will measure the volts and amps but probably best just to take it to a specialist I guess. The boat is on the Hamble. I live near Oxford. Any recommendations?

Thank you everyone

What make is the alternator ?

 

[BobnLesley]

I'd check the ground wire(s) first. I once had similar on a motorbike: The diode board earth wire had a dry joint and as the vibration increased, along with the revs, the problem got worse. If that's not your problem, then I too would be looking at/testing the diodes next.

 

[Shaz77]

It may just be the carbon brushes (if fitted)

If they know how to that's worth a check, car alternators usually come apart but boat alternators in a salt environment could be a problem and if they don't know how to strip the thing down, and with today's hourly rate, it may be cheaper to chuck a secondhand or new one in. I don't know what engine it is or rated amp.

 

[Shaz77]

I'd check the ground wire(s) first. I once had similar on a motorbike: The diode board earth wire had a dry joint and as the vibration increased, along with the revs, the problem got worse. If that's not your problem, then I too would be looking at/testing the diodes next.

You must not come off subject. This is not a motor bike forum

 

[PaulRainbow]

If they know how to that's worth a check, car alternators usually come apart but boat alternators in a salt environment could be a problem and if they don't know how to strip the thing down, and with today's hourly rate, it may be cheaper to chuck a secondhand or new one in. I don't know what engine it is or rated amp.

Judging from the amount of "salt environment" comments you make, you must really have a damp/wet/smelly boat.

A boat alternator is in a nice warm engine compartment, away from salt spray. A car alternator is under the bonnet, out in the fresh air, exposed to the weather and road grit spray.

The regulator/brush holder on a typical alternator is held on with 2 screws. The local village idiot could check them/change them.

 

[DoubleEnder]

It’s a Yanmar 1GM10 engine. Not sure of the make of the alternator, but is going to be something pretty basic. I’ll be back on board in a day or two with a meter and see what I can deduce. I’m pretty ignorant of electrics. Is the diode board inside the alternator or external?

 

[Boater Sam]

Practically all are internal these days and usually part of the regulator.

 

[Stemar]

The regulator/brush holder on a typical alternator is held on with 2 screws. The local village idiot could check them/change them.

Maybe the village idiot could, but I've sailed with intelligent people who couldn't. My last boss, an extremely competent deputy director of finance for a large NHS trust, freely admitted that, with a screwdriver in his hand, he became a public danger.