the diode is something like 100 piv 1 amp, and put in line with the banded
end toward the alternator. in the brown yellow lamp indicator wire directly
at the alternator, you can crimp some connectors on the diode and use some
heat shrink tubing so restoring it to the original form would only take
seconds.
I should explain that I put it in because my car would run on for 10 minutes
after I shut it off, not because of any charging problem. I had 9 or so
volts coming out of the alt indicator terminal (which is not normal in my
opinion), which was keeping the ignition relay on. the basic functionality
of the diode prevents this dc voltage from the alt reaching the relay coil.
however I now think that the re-introduction of the ignition relay in my
'77, (the po had chopped it out), and maybe the introduction of a
solid-state point replacement (ignitor), may of had something to do with
this. (and yes it is all wired correctly), I did jump start the car at the
same time so I am not really sure. perhaps the original
points/coil/resistor/resistor wire/lucas elec ignition combo had a larger
load on the circuit and pulled down that 9volts which as I said would
dissipate by itself after 10 minutes. that would mean that the basic wiring
design was somewhat marginal (being polite). I would not put the diode in if
you have charging problems, maybe a voltmeter would be a better idea. the .6
dv drop may disguise the real error and give you a false sense of security.
If you know someone with an scope you can look at the waveform and see if
there is a lot of AC on that line, or perhaps just put an ac voltmeter on it
and see if there is any ac, (which would mean a shorted diode).
after the diode installation the falsely labed ignition light would come on
and off like it should.
my ignitor works fine, so does my msd system. (and the tach).
If the lamp glows at idle then that is the characteristic low charging rate
indication, and usually means something else, slipping fan belt, or
something really wrong with the alternator. there are some really excellent
old time books on charging systems by the 'old guys' that I used to use at
one time, they used devlish tricks like with everything off, measuring the
resistence between the battery terminal and the alternator ternimal. then
the grounds, then through the ignition switch. what I would find would drive
me nuts, (big resistences) where theoretically there should be nearly none.
if everyone did such stuff it would be a happier world.
now if you want to install a real manly alternator, like a 65 amp bosch unit
like god intended instead of the pansy 34 or 43 amp circa 70's one that only
puts out at 1600 rpm, something you can be proud of, well , that's something
else again. (I was thinking of going for 90, that one is only a tad bigger,
but I got ahold of myself just in time).
I used to put chrylser alternators and regulators regularely on jags in the
shop I worked in. worked very well too. the owners all liked the savings. I
will certainly fry in hell in suppose.
----- Original Message -----
From: Fred Pixley <fpixley@kingston.net>
To: mgs-digest list <mgs@autox.team.net>; <teds@accessone.com>
Sent: Thursday, February 11, 1999 4:35 AM
Subject: : Alternator light
>I'm inclined to accept your theory and would ask where the diode is
>positioned in the circuit exactly? Also what direction is it oriented? I
>would assume you position it to allow current from the alternator but
>prevent leakage back to the alternator.
>
>
>>Date: Wed, 10 Feb 1999 17:39:12 -0800
>>From: "teds" <teds@accessone.com>
>>Subject: Re: Alternator light
>
>
>>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.
>
>
>
>Fred Pixley
>Napanee, Ontario, Canada
>
>
>
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