Does anyone know exactly how the regulator in a 1967 and earlier MGB
works?? I have a voltmeter and an ammeter installed in my car (I did
that myself about 6 years ago), and have been experiencing some odd
readings. And this is with a new generator and new Lucas regulator. As
far as I can remember, from my Chemical Engineering Process Controls
training of some 10 years back, it looks like the regulator has a hard
time setting the gains it needs. The climate here is very cold (I am in
High Plains desert Idaho - lows about 10F, and highs about 20-250F
lately), and there are a lot of hours of dark (i.e. the car basically
has the lights on any time it is running). Here is what my system does:
When I leave work, I keep the low idle of the choke up above 1200 rpm,
so I can always be generating. No problem for about 5 minutes.
When I hit the freeway (speed limit 75mph), my car has warmed up, but
the ammeter is reading negative. The voltmeter gets down to about 11
volts, and the lights are dim. I keep the heater off for the time
being.
After about 10 minutes on the freeway, the regulator starts cycling in a
high amperage mode. This makes the lights go bright for a couple
seconds, and then dim for about 10 seconds. This continues for about 5
minutes. And gets the battery up to about 13 volts.
Somewhere, the system settles down, and has a net positive all the
time. I can even run lights, heater, and wipers and keep 14 volts
(which I understand is the specified high voltage level the system is
supposed to produce).
When I get home (it is a 30 min drive), all is fine, at 14 volts, and I
turn the lights off, make sure the charge is up, and shut down.
Not during any of this do I see the red light come on indicating a
charging system failure - and I know the light and circuit work, because
it does come on when it is supposed to on other occasions (for example
not running with the key on).
I suspect another new regulator would take care of it, or I could
replace the whole system with an alternator (although they put out more
amperage than my +/- ammeter can measure), but I'm really just curious
about why the system does this. It does it every day.
Phil Bates
'67 MGB - tempory winter car.
'58 MGA - lousy winter car - bad window sealing
misc. other cars, one of which I wish would be my winter car and not
cost so much to keep in good repair.
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