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Post by lollygagger on Nov 28, 2017 9:38:34 GMT
Get a new generic alternator and try it? If it doesn't work either then put old one back and find what the problem was then just keep the alt as a spare. I had a similar problem on a 20 year old alternator which was just very dirtyand nackered I just replaced it and all working now. Didn't really seem worthwhile refurbishing it as a new one isn't expensive anyway, unless its a special alternator. Mine was an a127 type. Shame on you! Replace parts until it works is the modern way I suppose but I've sold (fingers crossed) the boat and don't need spares. Happy to replace, but only if I know it needs it.
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Post by lollygagger on Nov 28, 2017 9:40:47 GMT
I replaced the 40 year old alternator on my camper then found it was a bad earth. After that I should have learned not to rush into these things.
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Post by Deleted on Nov 28, 2017 9:44:41 GMT
I agree with this principle but the alternator was fucked and I don't have workshop facilities to refurbish myself and am allergic to paying someone else to do these things. The alternator was very nackered BTW and a new one sorted it. It wasn't wiring as I checked that by removing and refitting the original alternator before replacing
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Post by Deleted on Nov 28, 2017 13:22:13 GMT
How many hours has that alternator done? You mentioned the possibility of worn brushes earlier. It could be that. If they were badly worn you'd probably find it will struggle with large loads (check ammeter) and you may see the bulb flickering faintly at low revs. "If" it is the original engine alternator it was second hand 30 years ago... The boat is as good as sold but I'd still like to sort out this problem before I hand it over. If so, I would imagine the brushes are knackered now. I think some places still test and refurbish alternators. Basically put new brushes and diodes in if needed. Might work out a bit cheaper than buying a new one.
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Post by lollygagger on Nov 28, 2017 13:26:26 GMT
"If" it is the original engine alternator it was second hand 30 years ago... The boat is as good as sold but I'd still like to sort out this problem before I hand it over. If so, I would imagine the brushes are knackered now. I think some places still test and refurbish alternators. Basically put new brushes and diodes in if needed. Might work out a bit cheaper than buying a new one. I've now consulted my paperwork (marina/broker had it) and there's a bill for replacing the alternator two years ago.
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Post by lollygagger on Nov 28, 2017 13:40:14 GMT
I'm selling no.1 boat. It needs a fair few revs to get the charge light to go out. I don't like to do this to a cold engine so I warm it up first, but it won't look good to a prospective purchaser and the boat shakes a bit! It needs more revs than I would ever use under way, it's an old Perkins 3 cylinder with a big prop. Q. How to make it go out at lower revs? A bigger bulb (more watts). I'll check what's fitted when it stops raining. Once the light goes out, does it stay out at idle? If so you should be able to improve things by sending more current through the lamp circuit. If it comes back on as soon the revs drop, the issue is a more fundamental one - pulley ratios, faulty alternator, loose belt etc. But presuming the former, you can try a higher wattage bulb. Some people put a wirewound resistor in parallel with the bulb circuit as an alternative to a higher wattage bulb. Maybe 47 ohm 5 watt ceramic resistor. It will get very hot with the ignition on and the engine not running so bear that in mind when locating it. I the boat has had a split charge relay added, this can sap current that would otherwise go to kick start the alternator and the standard solution to that is the higher wattage bulb or resistor in parallel. This of course presumes its a standard alternator excited via the warning light. It probably is, but not all are. After more investigations you may be onto something with the split charge relay. There is only one alternator (while the new boat is bristling with them) and there is a relay in behind the control panel, I can't think what else could be for. The single 200ah LB is ancient - 10 years or more old and known to be on it's last legs. But the same revs are needed even with it plugged in the 240v charger constantly. No rev counter but I'm pretty good at guessing and it ticks over very slowly, I'd say 400-450rpm. It probably doesn't need more than 1500rpm to extinguish the light but for this boat that's more than full speed on my local canal. More thinking out loud - there are two wires on one side of the bulb. Ah-ha - classic place to pick up the signal for a split charge relay. I shall go and look harder and if it is for that will disconnect the relay wire and give it a try.
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Post by JohnV on Nov 28, 2017 13:50:22 GMT
Once the light goes out, does it stay out at idle? If so you should be able to improve things by sending more current through the lamp circuit. If it comes back on as soon the revs drop, the issue is a more fundamental one - pulley ratios, faulty alternator, loose belt etc. But presuming the former, you can try a higher wattage bulb. Some people put a wirewound resistor in parallel with the bulb circuit as an alternative to a higher wattage bulb. Maybe 47 ohm 5 watt ceramic resistor. It will get very hot with the ignition on and the engine not running so bear that in mind when locating it. I the boat has had a split charge relay added, this can sap current that would otherwise go to kick start the alternator and the standard solution to that is the higher wattage bulb or resistor in parallel. This of course presumes its a standard alternator excited via the warning light. It probably is, but not all are. I shall go and look harder and if it is for that will disconnect the relay wire and give it a try. awaits with bated breath
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Post by lollygagger on Nov 28, 2017 14:30:11 GMT
Β I shall go and look harder and if it is for that will disconnect the relay wire and give it a try. awaits with bated breathΒ It's cold out... Oh gone on then...
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Post by lollygagger on Nov 28, 2017 14:45:56 GMT
Yes it was connected to the relay. The other wires are all big fatties so depite being unable to trace them I think it's safe to assume it's a split charge relay.
Removing the wire did bring it down to more acceptable revs - still a bit high for my liking but a big improvement.
Thanks all, that'll do I think. π
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Post by Telemachus on Nov 28, 2017 17:01:07 GMT
Yes it was connected to the relay. The other wires are all big fatties so depite being unable to trace them I think it's safe to assume it's a split charge relay. Removing the wire did bring it down to more acceptable revs - still a bit high for my liking but a big improvement. Thanks all, that'll do I think. π But if you leave the relay disconnected, one of the two battery banks (probably the domestics) will no longer be charged. You need to put the relay back in circuit and fit a bigger wattage bulb or add another bulb or resistor in parallel with the bulb.
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Post by peterboat on Nov 28, 2017 17:11:50 GMT
The bigger wattage bulb is the easiest and cheapest fix change you lazy bugger
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Post by tonyb on Nov 28, 2017 19:19:01 GMT
The bigger wattage bulb is the easiest and cheapest fix change you lazy bugger But in this case it will need a new lamp because a higher wattage bulb is not available for that holder. That in turn almost certainly means drilling the instrument panel. I'd go for a hidden bulb or resister in parallel.
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Post by lollygagger on Nov 28, 2017 21:53:38 GMT
I'll have time to sort it properly once we've been for a test drive which could be tomorrow. I don't think it's a deal breaker but I'd rather not start a run out by revving the nuts to get the light out. Nobody need ever know.
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