alternators again sorry

[haza]

alternator light keeps coming on so mister got it checked turned out it was faulty .so got a new one , still the light comes on ,,told it could be the starter battery.thats fine ..when the engine is revved up the light dims but does not go off .any ideas please thanks in advance 

[WotEver]

We need some voltages. When the engine is running what voltage is on the D+ terminal? What voltage is on the B+ terminal? Those figures will help with starting a diagnosis. 

[Tony Brooks]

One or two alternators, if two how many warning lamps, any additional controllers, how tight is the drive belt and is it the right size/profile as well as what the other Tony asked.

[Tony Brooks]

Further to the above. If you have one alternator and two banks then if the alternator is energised (D+) from the engine battery but the main charging lead runs to the domestic bank (B+) then a faulty or resistive (burned contact) in the split charge device could cause these symptoms.

 

In the scenario above the flatter the start battery is the brighter the lamp MIGHT glow but if the start battery actually starts the engine after standing overnight off charge I doubt there is anything wrong with it.

 

[MtB]

16 hours ago, haza said:

alternator light keeps coming on so mister got it checked turned out it was faulty .so got a new one , still the light comes on ,,

 

 

Never mind all the technical advice. Don't use this person again they are obviously clueless!

 

 

[haza]

who we on about mike

[WotEver]

24 minutes ago, haza said:

who we on about mike

The one who said the alternator was faulty. 

[haza]

it was put on an alternator test machine at the factory in front of mister and was shown where the fault was.  so was the one he brought .he took the new one back today and again it was put on said machine ,,,showed there was not a fault ..there top guy said there was a fault elswhere

[Tony Brooks]

which is why we need more information and voltages. At present any "diagnosis" from here will be educated guesses based on insufficient information so can not be trusted. When we get the voltages and know more about the boat the "guesses" will become more and more accurate.

 

One other test that might help. If you have some form of charge splitter so one alternator charges two battery banks then then putting a voltmeter across the two main terminals that carry the charging current and then starting and revving the engine with discharged batteries may help. Expect some voltage before starting but at an random value. Ignore this, but once its started the voltmeter should read all but zero. If not the higher the reading the more damaged the splitter be it a relay or diodes.

[haza]

ok thanks every one for the input not that we understood any of it. but much appreciated ..i dont think we can do much damage as we are on shoreline and will get it looked at after the hols ..merry xmass to every one and thanks again