My first guess would be a bad connection between the cable clamp and
battery post. This connection can pass enough for the test light, but
put a small load on it and it fails so the light goes out. Put a large
load on it and it can arc so the starter can turn.

It is unlikely you have a battery that flat dead if you can start it and
drive it for an hour after it 'takes' a charge. If the battery is bad
enough to show 0 for a test light, the charger shouldn't work.

Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
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Will wrote:
>
> OK, I am pretty sure it doesn't matter what specific car I have, other
> than that it is a 12 volt negative grounded vehicle, with a separate
> alternator, regulator, but I'll go ahead and say it... this is a 1971
> Citroen 2CV.
>
> Here are the two things I think are weird. The first may not be an
> issue, because I haven't tested any other cars to see if they do the
> same thing, but instinctively I think it's not right. When I put
> connect a test light from the postive to negative battery terminals,
> with the ignition OFF, the light lights up. When I turn the key, so
> ignition is ON, but the engine is not running, the test light does not
> light up. That just seems wrong to me, as if the ignition wasn't
> grounded or something. But you experts tell me.
>
> The second thing, that is more at the heart of the problem I'm having
> (charging system not charging the battery) -- is this. With this car,
> ignition OFF, the alternator's + terminal should have power, and
> indeed, the test light lights up. And, both the Field wire on
> alternator, and Field and Ignition wires on regulator all do NOT light
> up with ignition OFF, engine OFF.
>
> However -- with ignition ON, engine OFF, all FOUR of those wires light
> up! -- though, I would estimate that the + terminal of Alternator and
> the Ignition wire of the regulator are getting more volts than the
> Field wire on both Alternator and Regulator, because the light is
> brighter on the + or ignition wires.
>
> Now, someone advised me that in that last scenario, ONLY the Field
> light should be on unless the battery is discharged (granted, which
> mine probably is), but I still think there's something screwy going
> on.... My next step is going to be bypassing the harness and connecting
> wires directly between Regulator Field and Alternator Field, and
> Regulator Ignition to Battery Positive Terminal.
>
> Any tips/suggestions/name calling?
>
> Thank you,