As one who had put a diode in the line, when properly installed, it works
fine and so does the charging light and the charging system. what it cures
is a leaky or shorted diode in the regulator, which originally had the same
purpose. I can explain how current flows with a diode if anyone is
interested. Since the diode was free and a new regulator pack wasn't it
seemed like a good idea to me.
I learned about the diode bit from various mg shops in this area who were
surprised that as an MG owner I didn't, and lots of time/money spent
researching/rebuilding the electrical system, I had no desire to spend
invest money in lucas electrical parts of that era. I have since replaced
the alt with a bosch alternator which works very well indeed, it will
probably outlast the car. my original problem occured after jump starting
the car, which had a flat battery due to leaving something on. Since I might
jump start the car again in the unforseenable future, I didn't want to take
the chance of whacking the lucas alternator again.
----- Original Message -----
From: Florrie & Allen Bachelder <bachldrs@swva.net>
To: Paul Hunt <paul.hunt1@virgin.net>
Cc: <mgs@autox.team.net>
Sent: Wednesday, February 10, 1999 4:26 PM
Subject: Alternator light
>>...Fitting a diode in the indicator lead to cure this is absolutely
stupid -
>>all you are doing is stopping your alternator telling you when it has
failed
>>completely, it would be far simpler to remove the light altogether. But
the
>>preferred option is to fix the real problem.
>>
>>PaulH.
>
>Paul - and List -
>
>Maybe it is ...absolutely stupid... but I can duck that one 'cause I'm not
>the one who did it. At any rate, the offending diode is no longer there.
>But even then I ask why, when the diode was still there, did the light
>still come on brightly when switching on the ignition (as it is supposed
>to), only to promptly quit when the engine started (again, as it is
>supposed to)? Why did the diode not prevent it from lighting at all?
>
> As I think about this, I may be starting to answer my own question.
>Hopefully you can either verify or show me the error in my thinking. The
>light simply indicates a voltage desparity between alternator output and
>the ignition circuit, right? What if the alternator output voltage is
>slightly higher than that (from the battery) at the end of the white wire?
>The light would glow then too, right? But since that is not due to an
>alternator fault, we don't need that information. So, (1) can we defend
>that in-line diode on the basis that, since it allows current flow in one
>direction only, it is simply keeping the light off when the alternator
>output is greater than the ignition circuit, and (2) is there a type of
>battery defect that can lower its output enough to cause this problem (the
>glow is rpm-independent)? I would presume that if this is due to line loss
>from poor contact in a bullet connector or the ignition switch, that in 23
>years, total failure would have resulted.
>
>I suppose another answer that it apparently is charging - enough to be
>functional even - but not as much as it should. This battery, of
>indeterminate age when I bought the car in '91, still spins the starter
>faster than any of my other Bs.
>
>But really, despite the fact that we all know the light isn't supposed to
>glow, if the car is operated that way without electrical failure for over
>two years and perhaps 20,000 miles - mostly commuting at hours when the
>headlights are on - is it not unreasonable to presume that there is no real
>problem?
>
>Oh-oh - I should never talk that way - lest tomorrow morning I should go
>out to start my B and find the battery dead.
>TIA
>
>Allen
>
>
>
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