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Post by ianali on Mar 30, 2021 13:20:10 GMT
So I’ve had a look. Taken readings across b &d positives. Virtually reads nil, or near as damn it. This is with engine running at various rpm. It reads battery voltage with engine turned off. Back of alternator has D+. B+ both connected as expected. W terminal not used. Then it gets interesting, a green wire from alternator that goes no where? Hasn’t come away, it’s simply blanked off. And...there is no ground wire at all. The owner remembers that when it was fitted around two years ago, the sparky said no ground required as it would be ground through the alternator clamps. So thoughts please? It is normal for the alternator casing and mounting brackets to act as the negative connections. You can get marine alternators with isolated negatives (requiring a separate negative connection) but these are uncommon on canal boats. Where on the alternator is the green wire connected? Although as you say, this has probably never been used. Did you confirm that the voltage directly across the batteries with that engine running, was 15 volts? Because of course a faulty measuring device is one possibility. If so I think we must conclude that the alternator regulator is faulty. Yes measured 15v with my meter, backed up by meter on inverter/charger and BM-2. Thing is though, as soon as fridge was turned on it drops around 14.2-14.5 and doesn’t doesn’t really get higher again between fridge clicking in and out. I’m thinking maybe it’s always been this way. Anyway. To warm to mess in engine room anymore. I suppose best way is to pull the alternator out and send for check/repair. Thanks for taking the time and give our best to Jeff.
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Post by Telemachus on Mar 30, 2021 13:23:13 GMT
It is normal for the alternator casing and mounting brackets to act as the negative connections. You can get marine alternators with isolated negatives (requiring a separate negative connection) but these are uncommon on canal boats. Where on the alternator is the green wire connected? Although as you say, this has probably never been used. Did you confirm that the voltage directly across the batteries with that engine running, was 15 volts? Because of course a faulty measuring device is one possibility. If so I think we must conclude that the alternator regulator is faulty. Yes measured 15v with my meter, backed up by meter on inverter/charger and BM-2. Thing is though, as soon as fridge was turned on it drops around 14.2-14.5 and doesn’t doesn’t really get higher again between fridge clicking in and out. I’m thinking maybe it’s always been this way. Anyway. To warm to mess in engine room anymore. I suppose best way is to pull the alternator out and send for check/repair. Thanks for taking the time and give our best to Jeff. Thanks, will do. So it just sounds like the alternator regulator is a bit “leaky” and if a small load keeps it happy, at least the chap can go boating for a while before needing to fix it.
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