DWADE REINSCH wrote:
>
> Here's a wiring/ignition question. Sometimes when I shut off my 77 MGB,
> it stops immediately. But sometimes it continues to run. When I turn
> off the key, the red "ignition" light glows MEDIUM, but the engine
> continues to run. Sometimes I flip the key on/off/on/off and it stops,
> sometimes blip the throttle, sometimes flip on the headlights, and then
> it will stop. Notice: Whenever it decides to stop running, the red
> "ignition" light immediate turns from medium red to bright red.
It is normal for the ignition light to glow somewhat while the engine is
running down after the ignition is turned off. However, the engine
should eventually run down, whereupon the ignition light should go out.
Is the engine coughing and spluttering after you turn the ignition off
or running normally? I suspect the latter. Are you saying the ignition
light is still bright when the engine has eventually stopped and the
ignition key is out of the lock?
If the answer to both is 'yes' it sounds like an alternator internal
diode problem - generating enough voltage via the ignition light to keep
the ignition circuit partially powered - i.e. enough to hold the
ignition relay in. Turning on the headlight increases the load on the
alternator which reduces its output enough to release the relay.
PaulH.
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