In my experience a disconnected ignition warning light will still allow the
alternator to charge but the engine may have to be revved to 2k or 3k to get
it to start. Once started it works normally unless the revs drop below
about 300rpm, at which point charging ceases and the engine has to be revved
to get it to start again. This is with a used alternator, it may not happen
with a brand new alternator out of the box. I tend to think that this is
due to a certain amount of residual magnetism in a used alternator
performing the function of the warning light (the initial excitation of the
field winding) much like it does in a dynamo. However, unlike a dynamo, an
alternator MUST NOT be flashed across 12v as it may well destroy the diodes
and regulator.
The ignition light should light up when the ignition is first switched on,
and go out again when the engine is started and revved to about 900rpm.
Additionally, you may also notice that it glows again when the ignition is
switched off but the engine is still spinning, until the engine finally
stops. This, along with the tach (electric), is a useful faulting
indication if the engine cuts out while you are driving along. However this
latter glowing will not happen if a diode has been fitted in the warning
light circuit to stop running-on (normal running, not Dieselling) on late
cars with an ignition relay and an after-market alternator.
PaulH.
----- Original Message -----
From: <mgraziano@mindspring.com>
To: Tom McLaughlin <tmcl98@yahoo.com>
Cc: <mgs@autox.team.net>
Sent: Tuesday, March 07, 2000 7:49 PM
Subject: Re: Re: Alternator?
> I'm not sure how it is on the B's, but on my Midget the alternator will
not charge the battery if the ignition warning light (and alternator not
working light) is burnt out. That would be the red bulb on my dash. Does
the red light light up when you have the car on jumpers, and you put the key
in the ignition?
>
> Can anyone confirm this?
>
|