Duff alternator?

[Stemar]

Not many years ago, my alternator died and I got another one from an auto electrician. It always took a bit longer than I was used to for the warning light and buzzer to go out, but the supplier had closed down, so no chance of taking it back. Last year, it got worse, and I'd have to go to near maximum revs for it to energise, so I had it checked. It was given a clean bill of health. so back it went and, while still slow to kick in, it did charge the batteries perfectly well.

A couple of days ago, I visited the boat to check things over, and ran the engine which, being a fairly venerable VP2003 that hadn't run all winter, was slow to start, but got there and ran happily. Apart that is from the alternator. The light and buzzer wouldn't go off, even at full revs in neutral, and the voltage on the domestic battery was 13.3V, about the same as before starting. (I have 40w of solar panels, which keep things fully charged, even in winter.) I haven't got the standard VP panel, the charge warning light, a simple filament job, has a 12V supply and is earthed to the field terminal on the alternator. It's a system that's worked well for many years. The light is at its usual brightness, which suggests there is no problem with corrosion in the circuit, and the belt is in place.

Is there anything other than a duff alternator that could cause these symptoms?

 

[TernVI]

Some alternators have distinct 'Field' and 'Warning Light' terminals.There may be other terminals. Is it wired up correctly?

 

[VicS]

Not many years ago, my alternator died and I got another one from an auto electrician. It always took a bit longer than I was used to for the warning light and buzzer to go out, but the supplier had closed down, so no chance of taking it back. Last year, it got worse, and I'd have to go to near maximum revs for it to energise, so I had it checked. It was given a clean bill of health. so back it went and, while still slow to kick in, it did charge the batteries perfectly well.

A couple of days ago, I visited the boat to check things over, and ran the engine which, being a fairly venerable VP2003 that hadn't run all winter, was slow to start, but got there and ran happily. Apart that is from the alternator. The light and buzzer wouldn't go off, even at full revs in neutral, and the voltage on the domestic battery was 13.3V, about the same as before starting. (I have 40w of solar panels, which keep things fully charged, even in winter.) I haven't got the standard VP panel, the charge warning light, a simple filament job, has a 12V supply and is earthed to the field terminal on the alternator. It's a system that's worked well for many years. The light is at its usual brightness, which suggests there is no problem with corrosion in the circuit, and the belt is in place.

Is there anything other than a duff alternator that could cause these symptoms?

Maybe the regulator is failing. Worth getting the alternator checked again perhaps

If alternator and regulator check out ok may be a a larger wattage bulb , or a 50 ohm resistor in parallel with it, will kick the alternator into life at a lower rpm.

 

[Stemar]

Thanks, everyone.

I don't think the alternator has any "spare" terminals, but I will check I haven't done something stupid like connecting the warning light to the W terminal! I don't think I have, because the split charge relay (not VSR) is fed from the same connection as the warning light, and the domestic voltage went up when the light eventually went out.

 

[andsarkit]

You could check the carbon brushes. That might be easy as some car ones come out with the regulator. With my Nippon one you have to take the end off the alternator and then put a rod through a tiny hole to hold back the brushes as you re-assemble it.

 

[VicS]

You could check the carbon brushes. That might be easy as some car ones come out with the regulator. With my Nippon one you have to take the end off the alternator and then put a rod through a tiny hole to hold back the brushes as you re-assemble it.

Doesn't the fact the waring light is on at its normal brightness indicate that the brushes are OK

 

[TernVI]

Thanks, everyone.

I don't think the alternator has any "spare" terminals, but I will check I haven't done something stupid like connecting the warning light to the W terminal! I don't think I have, because the split charge relay (not VSR) is fed from the same connection as the warning light, and the domestic voltage went up when the light eventually went out.

So now you drip feed the information that there's a 'split charge relay' added.
That would appear to be significant difference between the alternator working when tested on the bench and not working in your system?
Test the alternator on the boat with the minimal set up.
12V battery, warnng light, volt meter.