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Date: Sat, 09 Aug 2008 15:32:51 -0400
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From: Jim MacKnight <jmacknig@cisco.com>
Organization: ATG Hardware Engineering
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Subject: Re: [LML] Re: Overvoltage
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I had similar issues with my 320 about 1-1/2 years ago.  Would work fine 
until the charging system would just drop off line.  Contacted B&C and 
they helped me go over the basics (intermittent in the field lead, bad 
OVP, loose battery cable, bad regulator, broken regulator circuit board, 
intermittent BAT/ALT switch connection, etc.).  Also had the alternator 
tested locally at maximum load (90A) for over 10 minutes with the 
suspect regulator.  Nothing found.

Finally was able to troubleshoot it with a portable DMM and captured 
that it truly was an OVP event (~50msec spike) causing the regulator to 
trigger.

Final cause & fix.  Found the alternator brushes were worn (to ~1/2) and 
was getting "brush hop".  The brushes would hop up just long enough 
(>50msec) for the regulator's OVP to trigger.  This would occur at 
various rpms & electrical loads.  One of the tell tales was it would 
occur at lightt electrical amperage loads -- by increasing the 
electrical load, it would delay the OVP event.  Fix was to replace the 
$20 set of brushes.  At that price I bought a new pair for next time :)

Hope this helps or gives someone else ideas for the future
jim...

Alain NOIREAUX wrote:
> Steve ,
> could you put the paper from Bob Nucholls on LML ? It could interest a 
> lot of people to check their electric system . Many thanks
> Alain Noireaux   L 320  F-PSDV
> John Schroeder a écrit :
>> Steve -
>>
>> What size battery cables do you have?  How long are they (battery to 
>> Alternator & battery to DC busses)? A crimp anywhere in the system 
>> when exposed to heat and very cold temps we can get in the winter may 
>> be the culprit. Corrosion in the big terminals may be a problem. 
>> Ground straps can get frayed or corroded.
>>
>> What regulator do you have? Internal to alternator or external? Our 
>> B&C regulators have a built-in over voltage circuit that has a 
>> specific test to determine if it is working - at that particular moment.
>>
>> I'm sending you, in another email, a test paper that Bob Nuckolls 
>> wrote on how to check out the alternator/regulator/battery system. It 
>> may help. We installed a jack for each alternator to make this test 
>> easier.
>>
>> I  don't mean to be preachy - just some ideas for what must be a very 
>> frustrating problem for you. Hope this helps.
>>
>> John
>>
>>
>> On Sun, 03 Feb 2008 03:00:12 -0500, Steve Reeves <sreeves@sc.rr.com> 
>> wrote:
>>
>>> The other battery was fine, and I just bought a brand new B&C but
>>> still have the same problem.
>>>
>>> Steve
>>>
>>>
>>>
>>> At 07:14 PM 2/2/2008, you wrote:
>>>> check your battery.
>>>>
>>>
>>
>>
>>
>>
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