andyfish Posted September 7, 2014 Share Posted September 7, 2014 How do,during our last Holiday on Bobella one of the two battery warning lights came on and stayed on The boat has 2 alternaters charging 4 domestic batteries and one starting battery in a bank of 3 and a bank of 2 Any ideas Andy Quote Link to comment Share on other sites More sharing options...
andyfish Posted September 7, 2014 Author Share Posted September 7, 2014 Forgot to mention when I rev the Engine the Light will pulse and the needle on volt meter goes up and down,when I shut the revs down the light dims Andy Quote Link to comment Share on other sites More sharing options...
BrundallNavy Posted September 7, 2014 Share Posted September 7, 2014 You need to check with a meter the battery voltage with the engine off and again with it running, if no increase is seem then the alternator is defective or you have a wiring fault. Doug. 1 Quote Link to comment Share on other sites More sharing options...
andyfish Posted September 7, 2014 Author Share Posted September 7, 2014 I put volt meter on when running and volts go up to 14 ish volts Andy Quote Link to comment Share on other sites More sharing options...
finny Posted September 7, 2014 Share Posted September 7, 2014 The first thing I would be checking Andy is all the wiring connections and get a drop test on the batteries ,it could be something as simple as a bad earth before you work backwards towards the Alternators and charging systems which is will be the more expensive end of the problem Finny 1 Quote Link to comment Share on other sites More sharing options...
mbird Posted September 8, 2014 Share Posted September 8, 2014 Might be a silly suggestion, but have you checked the belts? If one is slipping when the alternator is under load it could give the symptoms you have. 2 Quote Link to comment Share on other sites More sharing options...
diesel falcon Posted September 8, 2014 Share Posted September 8, 2014 sounds like your diode block,on the alternators packed in, sounds as though it,s still charging at 14volts though trace the conection from the light to the alterntor, if ok change diode block(removal required and repair shop) Quote Link to comment Share on other sites More sharing options...
Viking23 Posted September 8, 2014 Share Posted September 8, 2014 Yes if the connections are ok, and the belts are not slipping, then the alternator is more likely at fault. However if the battery is unable to take any charge, ie Kaput (not my normal technical term for a duff battery lol) then this could cause similar symptoms. If it is the alternator, then it could be any of the diodes, or it could be the regulator. Some diode faults (but not all) lead to the alternator drawing current from the battery when the engine is off, sometimes as much as 4 amps, so you can also check for this too. Incidentally, another fault finding tip, NOT relating to this post, but if for some reason the ignition bulb doesn't light, because it had blown, then the alternator may not give any output, as it relies on the small current through the bulb to excite the windings of the alternator, so when the alternator starts to charge, the voltage on the exciter winding increases, and the bulb goes out, as the voltage each side of the bulb is more or less the same. I just felt that might help for future diagnostics. 3 Quote Link to comment Share on other sites More sharing options...
Hockham Admiral Posted September 8, 2014 Share Posted September 8, 2014 Welcome back, Viking! Quote Link to comment Share on other sites More sharing options...
andyfish Posted September 8, 2014 Author Share Posted September 8, 2014 Thanks for all your replies,Belts are tight so will check tother items when am next down Andy Quote Link to comment Share on other sites More sharing options...
Viking23 Posted September 8, 2014 Share Posted September 8, 2014 Welcome back, Viking! Thanks for the welcome, and great to see a few likes of my earlier post. I hope to make some good contributions. 2 Quote Link to comment Share on other sites More sharing options...
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