[Mgs] MGB alternator

[mgbob at juno.com]

Hi Paul,
  12,272 did not seem all that far to me either, especially when I recalled
that an alternator on my '75 had more than 200,000 while I had the car.
   This unit is one I got from a boneyard. It served for a couple of years,
then I replaced diodes. That was, however, at least five years ago and I do
not recall which of the diode packs I used. It's on the car now. If we are
confined to home this weekend by the hurricane coming up the coast, I will
have time to remove and open the unit.
Bob

---------- Original Message ----------
From: "Paul Hunt" <paul.hunt1 at blueyonder.co.uk>
To: <mgbob at juno.com>, <mgs at autox.team.net>
Subject: Re: [Mgs] MGB alternator
Date: Fri, 26 Aug 2011 08:47:32 +0100

12k isn't far at all, on a 'normal' car that is barely a years driving.  If
you replace just the diodes then there could be something else wrong with it
that is causing the diodes to fail prematurely and it will happen again.
OTOH if you get a rebuilt that came in with faulty diodes they may only have
replaced those and done a quick voltage and current check (perhaps).  I'd
prefer to keep original, so unless this is the second or more *replacement*
set that has failed, I'd change the diodes again in the hope that the
previous set was a rogue, otherwise get a rebuilt.

Incidentally what type of diode pack is it?  If it's the earlier type with
the nine visible diodes on large cooling plates, as opposed to the 'solid'
alloy housing with cooling fins, then it could be vibration causing the bond
between diode and plate to fail.

FWIW.

PaulH.