New electrical (ammeter) issue....

[Kansan]

Hey guys, I've had my cuda for about a year...nice driver condition '73. Never had an issue with battery until last week. I had the battery disconnected for a few days while doing some routine maintenance. When I hooked the battery back up, it was dead. No big deal I'm thinking, battery was in the car when I bought it and have no idea how old it is. Anyway, I threw a charger on it and let it sit all night but it wouldn't hold a charge. Grabbed a battery at wally world, no problem. However, when I took it out on the road I noticed the ammeter was pegged out to the "charge" side. After a mile or to, it dropped to about 3/4 guage then settled down to the middle after a short bit. Seemed fine the rest of the drive. This was on Friday. Took it to a show on Saturday and noticed the same thing. Electical issues aren't really my forte, but I can muddle through them. I have heard these old ammeters can cause issues and potentially very serious problems....like fires. Does this ammeter behavior sound familiar with anyone?

Thanks,

Kansan

 

[Challenger RTA]

Alternator is probably going bad. When the battery is connected there is always power the alternator. Ergo draining through the short in the alternator. That is the better possibility. There could be others.

Get the battery charged up and disconnect the alternator black wire over night. Or take out the alternator and have it checked.

Voltage regulator going bad? It needs a ground to work.
A bad battery can be a problem. You fixed that. At lest you think you did. A new one can be bad too.
When there is a charging issue. If it is showing discharge or overcharge. It is hard to say what the problem is until it is diagnosed.

 

[Challenger RTA]

This is for stock Mopar charging system.

1:With the key in the off position should have on the alternator output battery voltage.

2:The field wires should both read zero we should have no voltage.

3: If there is voltage at the field wires with the key off, there is a wiring problem.

4: If no voltage here at the alternator output with the key off then we likely have either a dead battery or we have a wiring problem or blown fusible link.

5: With the key in the on position. there will be voltage at the alternator output, it's going to be lower than what it was with the key off, because the entire vehicle is energized. The voltage drop is going to be more you can still see it go from
12 and a half down to 11.7. Still going to have near battery voltage.

6: What's important. With the key on. The field wires should have voltage. It won't be full battery voltage but it's has power coming to the alternator and it will be a lot less on one side and one side is high. That's the inlet so that's power going into the field windings.
The other one, the one that's low is the output from the field windings.
The output from the field winding is what goes back to the voltage regulator.
The voltage regulator on this is simply a switch ( Remember it needs a good ground to function.) all it's going to do is connect this field terminal here to ground and when it connects it to ground electricity then flows through the field windings energizing it and causing the alternator to charge.

 

[Challenger RTA]

7: Run test: This is for stock Mopar charging system.
Before doing the run test you're going to want to connect directly to the field output terminal on the alternator with some sort of a jumper wire. You can remove the existing field wire if it helps you to get to it. Use a jumper wire that comes back to the battery and it's not connected to anything right now. Have the voltage meter connected to the battery. Just checking battery voltage 12.3 volts there abouts. By touching the jumper wire to the negative terminal.
Just grounding it you can hear the engine load up because it's pulling a load and the voltage runs up to 14. That tells you that when the field in the alternator is energized it's charging. The alternator is good. Now you know that it's not an alternator problem at this point. If it's not charging you have a no charge scenario but this passes then you know it's the voltage regulator or some wire to it. It's most likely the voltage regulator and that's all it takes to diagnose the charging system on one of these
Here again If the any ground is bad or loose. it won't charge correctly or reliability. They become phantom grounds that just keep haunting you! That being the Voltage regulator ground, chassis ground, engine ground, Bolts, bolt holes, nuts and mounting brackets. 99% of the time there overlooked. The whole car is a ground.
That's all I have to say about that!

 

[Kansan]

Good information. Thanks!