John M. Rogers" <rogersj@worldnet.att.net> wrote:
>This evening when my wife came home in the MGA, the
>ignition light stayed on when the ignition key was turned
>to off. When the key was turned to on ... the light went off.
>I disconected the main wire (from the battery) at the
>control box, (spark, spark) and of course, the ignition light
>went out. I plugged it back in and everything works
> normally?? Why?
>[snip]
>
Since the ignition light stayed on when the key was turned off
... then went off when the key was turned on ... faulty control box.
Why? ... you let some of the 'smoke' out of the control box? <g>
The 'sparks' stored in the batteries are constantly being used
by the other Lucas bits to produce 'smoke' ... the dynamo's job is to
generate 'sparks' for the batteries and its capacity to do this varies
with rpm of the engine, however it is rather simple minded and has
no idea of how many 'sparks' to send to the batteries ... sending
too many 'sparks' to the batteries will make them boiling mad and
they will stop storing 'sparks' altogether ... so the dynamo relies on
the 'smoke' in the control box, which is rather intellignet, to regulate
the the flow of 'sparks' from the dynamo to the batteries so that the
batteries only receive the flow of 'sparks' that they require ... the
'smoke' in the control box monitors how well it is doing its job of
regulating the flow of 'sparks' and is aware when the dynamo is not
producing enough 'sparks' or when the dynamo is producing to
many 'sparks' and, to get your attention, will 'excite' the 'smoke'
in the ignition light if either condition occurs.
All kidding aside ... this eve I will try and ascertain what state the
control box was in to cause the ignition light to be illuminated with
the ignition key off and to go off when the ignition key was turned
on ... perhaps a contact in the control box hung? ... removing
power reset the contact?
Larry Unger
'62 MGA MkII Roadster
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