Originally posted by hanleyclifford
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Alternator Diode Rectifier Woe
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Originally posted by ndutton View PostOf course. The alt isn't connected in series and doesn't feed-thru.
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Originally posted by hanleyclifford View PostIf I were to place an ammeter between alt+ and the #4 cable going to the main buss bar, using a shunt and a digital gauge, I should get a zero reading even if the battery charger is connected. Do you agree?Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Originally posted by ndutton View PostYes, as long as nothing else is connected to alt+.
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Originally posted by Dave Neptune View PostHanley, are the batteries good? And how/where was the charger hooked up?
I used a std 6/12V 2/10amp battery charger. I hooked it up to the output feed from the alt for the positive and to the main ground buss for the batteries, not the best way but most convenient due to access. The batteries were under a bunk and the engine was too and with the engine cover off both were exposed. I left the power switch to both and did this for 34 years. I also keep my battery in my hot rod hooked in the same fashion as the battery is under the seat. I clip to the output of the alt and an engine mount as both are exposed the the engine is not fully covered. No issues so far there either.
I would talk to another alt shop repairman to hear his opinion then tell him what you were told.
I kinda think the guy was trying to be impressive above his "paygrade" and knowledge. I've blown a few diodes in my time but never with a charger. This has peaked my curiosity.
Dave Neptune
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The ammeter I prefer and have onboard is a Gauss loop rather than a shunt. Its main advantage is zero added connections so therefore zero added failure points due to corrosion, vibration or looseness.
Waiting for the information this ammeter provides but I'm getting an idea what happened. More data first however.Last edited by ndutton; 12-30-2023, 09:36 AM.Neil
1977 Catalina 30
San Pedro, California
prior boats 1987 Westsail 32, 1970 Catalina 22
Had my hands in a few others
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Hanley, how old is your battery switch? Is it possible that a contact could be corroded or malfunctioning? Most of the time a diode blows is due to a surge from a quick off/on and usually from switching under alternator charging loads. Good switches have surge protection but it does not mean they can't fail.
Dave Neptune
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I think it more likely that the alternator failed due to corrosion of one or both slip rings, preventing current from getting to the rotor. Not a big deal to crack it open and clean the rings.
edit: Might as well replace the brushes while you're in there.Last edited by Al Schober; 12-30-2023, 09:46 PM.
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Originally posted by joe_db View PostAnother possible issue: If there is a problem with the regulator or how it is wired, it can end up always being on and thus drawing power and possibly causing damage.
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Originally posted by ndutton View PostThe ammeter I prefer and have onboard is a Gauss loop rather than a shunt. Its main advantage is zero added connections so therefore zero added failure points due to corrosion, vibration or looseness.
Waiting for the information this ammeter provides but I'm getting an idea what happened. More data first however.
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Originally posted by Dave Neptune View PostHanley, how old is your battery switch? Is it possible that a contact could be corroded or malfunctioning? Most of the time a diode blows is due to a surge from a quick off/on and usually from switching under alternator charging loads. Good switches have surge protection but it does not mean they can't fail.
Dave Neptune
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Originally posted by Al Schober View PostI think it more likely that the alternator failed due to corrosion of one or both slip rings, preventing current from getting to the rotor. Not a big deal to crack it open and clean the rings.
edit: Might as well replace the brushes while you're in there.
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Originally posted by hanleyclifford View PostI am aware of that possibility but it is unlikely in my case where I have a solid state regulator (Transpo V1500) which has pilot lights for all functions. Also my ammeter is always on since the system is live at all times. On the mooring there is no problem but on a dockside charger even if you are showing no amperage at rest the possibility still exists that a parasitic draw is being balanced by the charger and concealing the problem. Both failures have occurred while on charger dockside or in the barn. As Neil has suggested I am going to start monitoring amperage at alt+.
OK, there is another way - a charger with a substantial AC component to the output might possibly do this. One would think the battery would smooth this out or the charger would just burn up, but in theory it might happen.
Jut thought of another way - if there is an AC tap for a tachometer or regulator signal, current might possibly go back in that way if there is some odd miswiring.Joe Della Barba
Coquina
C&C 35 MK I
Maryland USA
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