68 Silver Toy said: Can someone help me on this. My gauge on the car is telling me there is a discharge. Could it be a ground problem or alternator? When I put anything on like the heat fan or headlights on it shows discharge more. Thanks

My '69 is doing the same thing.  Always points to the left.  Am I running off the battery all the time?

Jim

Does the meter return to zero (straight up) when you turn off the car and turn everything off?

Yes, it always returns to zero when I shut her down.

An amp gauge that shows a discharge all the time(while running) indicates the alternator is not putting out enough juice to carry the load. This could be because the alternator is bad, or not rated high enough amp-wise. It could also mean a bad/loose connection. I would first determine how much voltage is at the battery terminals while running, and compare that to the voltage at the alternator while running. If both readings are low(at or below 12v), I would suspect the alternator.

The ammeter is essentially a voltmeter... Compares voltage at the starter connection and at the horn relay.  Higher voltage at the starter shows (+) amps, and vice versa.

Adam is right on.  What you can also do is connect your voltmeter at the battery with the car shut off (ignition on), note the voltage, then start the car and note the voltage again.  If the voltage goes up, it's charging and the ammeter may be bad.  If it doesn't change or drops a bit, you're not charging. 

In the "old days" people would start the car and disconnect the battery.  If the car died, it wasn't charging.  I was told that with modern cars (not that C3s are modern, mind you!) pulling the battery cable while the car is running could cause voltage regulator failure.  Anyone know if that's true?

Looks like its more electrical work for me.  Thanks to all for confirming.  I went out to disconnect the battery earlier and thought I'd start the car but we ran out of juice before it kicked over.  I'll check out loose wires as soon as it cools off out there.

If I check the voltage at the battery, won't I always get the voltage in the battery?

Jim

Please ring in on this.

If I need to replace the alternator, is there any problem with kicking it up from 63 amps to say 100 amps???

Checking the voltage AT the battery without it running will only tell you how much voltage the battery is storing at that time. What you are interested in is, is there  MORE than 12v there with it running? You should see at least 14v with the engine running, and no lights, or A/C, etc. on. Then check voltage AT the alternator, and see if there is MORE at the alt than there is at the battery. If there is, then you prolly have a bad connection somewhere. If the voltage is the same, your wiring is ok. Either way, if you do not see a minimum of 14v AT the alternator, engine running at around 1500 rpm, you have an alternator issue.

And...while it's true, we used to "test" alternators by  disconnecting the battery, it's not a good idea....it can definitely mess up a regulator, and/or the diode trio inside the alternator. Plus, that test doesn't really tell you how much the alternator is putting out....just that it is.
 It's best to use a volt meter.


Oh...and no...if you want to up the ante with a higher amp alternator, there's no problem with that. 100 amp might be overkill, tho....


|UPDATED|5/13/2013 7:50:15 PM (AZT)|/UPDATED|

Here's the scoop.  12 volts at the battery with engine off.  13 volts while running and 14 volts at the alternator while running.  But the battery meter shows -30 amps and goes lower if I gun the engine.

I guess I'm in the market for an ammeter, as soon as I figure how to remove the old one and how to test it for sure.

Yes, I'm troubleshooting two problems at the same time, horn and ammeter.  Don't think they're related.

Jim