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Old 11-10-2013, 10:42   #16
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Re: Can an alternator draw from battery overnight?

"I have heard that faulty diodes in the alternator can draw back. However, wouldn't that also mean that the alternator wouldn't charge?"
NO, if there is a "short" in the alternator's "rectifier" diode pack, of 4-6 diodes, it (the diode) will work perfectlly half the time. The output would be "dirty"... with some ac. Bearable to a battery and bulbs, and fixed when propertyly recharged. When engine/alt. is off, this shorted diode will continue to flow electricity drawing down battery. Measure the discharge rate, disconnect the combiner, then the alternator, looking for the current draw.
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Old 12-10-2013, 02:03   #17
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Re: Can an alternator draw from battery overnight?

Quote:
Originally Posted by Wraith_Mac View Post
El Guero,
The OP said in the initial post:
"I have tested the battery (which is just 12 months old) by disconnecting the leads over night & have also used a load tester on it. It appears to be holding full charge."
Cheers,
Mac
Missed that.

It can still 'be' the battery ... I have had one internal short on my life, it was a BEAST to finally find that problem.
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Old 16-10-2013, 23:57   #18
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Re: Can an alternator draw from battery overnight?

I got around to removing the alternator on the weekend & the auto electrcian declared it dead with multiple problems. He did say that it wasn't leaking but it also wasn't charging at all. I was there when he tested it on his test bench.

After pulling it down he said it wasn't worth repairing as it had already been done before & there were multiple problems & it appeared to have had a hard life. Not surprising since ours is an ex-charter Lagoon 380 with nearly 7,500 hours on the motors.

Anyway he has tracked down a 110amp alternator (to suit a Nissan 4WD) with the same mounting configurations & said that it will do fine.

The problem is I know the main Bat terminal is for the positive leads, & the Tee shaped plug is there also, but the lower terminal with 2 wires from the wiring harness on the old Hitachi is a mystery to me & doesn't exist on the new replacement. The auto electrician said that it was a 7 volt neutral for the Tacho etc & he wired a lead into the new alternator to provide this.

I do trust the electrician as he is very experienced, but can anyone confirm this before I hook it all up? I would hate to blow a brand new alternator or anything else.

Thanks

Dave
Seabreeze L380 #241
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Old 17-10-2013, 05:39   #19
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Re: Can an alternator draw from battery overnight?

See if this helps
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Old 17-10-2013, 10:28   #20
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Re: Can an alternator draw from battery overnight?

Thanks for that. However, none of those look anything like the original Hitachi 80amp setup.

Will try to take a photo on the weekend.

Dave
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