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Old 11th January 2020, 19:31   #21
Atlan
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I would query why you would expect to see an AC voltage across a heavy duty 12V DC battery.
Diode failures may also allow AC current to leak into the electrical system. AC voltage creates electrical “noise” that can confuse electronic modules and digital communications. A leaky diode also can allow current to drain out of the battery through the alternator when the vehicle is not being driven.
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Old 11th January 2020, 21:02   #22
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If a diode were to fail, how big would you expect the AC voltage to be ?
Is that figure in RMS volts, peak volts or peak to peak volts ?
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Old 12th January 2020, 13:05   #23
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If a diode were to fail, how big would you expect the AC voltage to be ?
Is that figure in RMS volts, peak volts or peak to peak volts ?
A good alternator should measure less than .5 V AC with the engine running.
Have a look here should should help you understand the basics
https://electrical-engineering-porta...harging-system
Would love to know where op got his replacement diodes from, if you have a link would be helpful to me also.
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Old 12th January 2020, 15:47   #24
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Quote:
Originally Posted by Atlan View Post
A good alternator should measure less than .5 V AC with the engine running.
Have a look here should should help you understand the basics
https://electrical-engineering-porta...harging-system
Would love to know where op got his replacement diodes from, if you have a link would be helpful to me also.
I'm the OP and I haven't yet ordered the regulator, I still haven't had time to look under the bonnet to see which version I have, but DMGRS sells both types.

Pete.
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Old 14th January 2020, 07:30   #25
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I would state that as the charging voltage is 14.6 volts, that there is nothing wrong with your regulator .
As the discharge current from the battery is less than 20mA when locked, there is no significant discharge through the alternator via short circuited alternator diodes (Open circuit diode conceivably)
So I would say there is nothing wrong with your alternator.
So I would revert back to there being an intermittent discharge from the battery, and the only one that I can think of (with the spec that you state) is the wipers.

Or search for a local supplier of goats blood !!!

PS Do you have a CD changer ? There have been reports of those spontaneously clunking away suddenly for no reason ?
And try disconnecting the Naval1. Being non-oem, I would suspect it may have been wired in incorrectly.

Last edited by MarkS; 14th January 2020 at 08:46.. Reason: CD changer
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Old 14th January 2020, 10:34   #26
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This is why I am scratching my head, none of it makes sense really.

No, there is no CD changer. I did wonder about the Naval, it was installed by me 5 years ago :-)
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