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Weird wiring for a weird car

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,

Reply to
Will
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Nothing weird going on there. Start with a new or charged battery. Your battery is so dead it barely supports a test light and goes off when the ignition is turned on. If you could invest in a $10 VOM you could measure this as it happened.

Reply to
Al Bundy

Really? I know this probably sounds naive, but hey, I have no problem sounding naive! :-)

When I tested this last night and got the results above, I had charged the battery, and driven maybe 20 minutes, tops. I've been finding I can drive at least 60 minutes on this charged battery, though admittedly I'm sure the battery's not in great shape from frequent charging/discharging.

I was thinking that the instant off of the test light was more due to a short or missing ground somewhere... but you really think it's a dead battery giving that result?

Thank you,

Reply to
Will

It would have to be one bad short and you would see the smoke and stink to go with it.

The battery is bad.

Reply to
dnoyeB

you can drive 60 minutes and then what? It quits? your charging system is hosed for one thing.

Reply to
ed

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 >
Reply to
Mike Romain

No, the light isn't lighting up because you are placing a heavy load on the battery. Either the battery is almost dead and unable to light anything other than that single test light, or you are placing something close to a dead short across the battery.

This does not correlate well at all with the earlier assertion up there that a light across the battery doesn't even light up when the ignition is turned on.

But, it's reasonable enough.

I'd go back and check and make absolutely sure that the lamp across the battery isn't lighting with the thing on. And if that really is the case, I'd try and find out why.

I'd also get a voltmeter, and measure battery voltage with the ignition off, with the ignition on, an with the engine running. That is really your first step.

And if the battery is good, but is being pulled down when you turn the engine to on, I'd check the ignition switch. As I recall it's fails in bizarre ways on the 2CV.

--scott

Reply to
Scott Dorsey

I *know* the charging system is not working. I've known that for a long time. What I'm trying to get at is the cause, because the alt is putting out voltage, and the regulator is new (though, granted, could be faulty), and the battery must be at least good enough to take some charge, otherwise I wouldn't be able to turn the engine over and drive around.

I thought not having any voltage showing up across the battery terminals was a good indicator of a short, or rather, a missing ground somewhere -- ignition switch was my inclination.

I started to trace each of the 4 wires from the ignition switch, but I don't think I know how to test a ground wire -- my test light won't light up when connected to a good ground wire, will it? What else can I do?

Thank very much for your help,

Reply to
Will

Connect one side of the test light to the positive terminal on the battery. If you touch the other side to a good ground, the lamp will light.

--scott

Reply to
Scott Dorsey

Somebody once said that if the only tool in your toolbox is a hammer, everything looks like a nail. Think about using a tool other than that one test light you have.

Reply to
Al Bundy

That should be: If your only tool is a hammer, every problem looks like a thumb. ;-)

But its the right idea. The test light can't tell you whether the battery is good, but dead and the charging system is hosed, or vice versa. Take the car to a shop with a charging system tester.

Reply to
Paul Hovnanian P.E.

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