Battery charging question

[JG1966]

Hello everyone. Looking for some help. My 72 Roadrunner 340 will not charge the battery. Staying at 12.6 V when off and when running. Battery, alternator are tested and good. Voltage regulator is new and grounded. But when car is running or when key is at "run" I get zero volts from both alternator fields and alternator main post. I've tried grounding green wire alternator terminal and started car to look for max voltage. Still nothing. I'm sort of new to electrical stuff and could really use some help to narrow it down. Thank you.

 

[Yatzee]

Obviously, you do not have 12v going to the alternator in the "run" position of the ignition switch. But you say you have 12.6 volts when the engine is off and running. This can't really be unless your reading the actual battery voltage at the "BATT" terminal of the alternator. I suspect there is an issue with the ignition switch. It is almost as though there is no 12v feed to the alternator to excite the windings thus no output from the alt. There also exists the possibility of other issues like poor ground, faulty wires, blown fuse etc. You really need a wiring diagram to trace color codes and supply voltages in that circuit. Don't be too sure that you don't have a faulty VR, battery or alternator. These are simplistic charging systems and are very easy to diagnose if you have the right electrical diagram.

Look here: http://www.mymopar.com/index.php?pid=28

 

[Mopars & Missiles]

 

[benrunner]

I had two new regs both bad I stuck an old one on and instant charging

 

[JG1966]

Thanks Yatzee. I am getting 12.6 V at the battery. I poorly worded it. I'm getting nothing at battery terminal of alternator. How can I test the ignition switch?

 

[Dreamcatcher]

Bad fuseable link in the wire going to the alt hot side?

 

[JG1966]

Thanx everyone. I'll do some more testing and keep you posted.

 

[coloradodave]

Here is one of many articles on how to test Mopar electrical systems on the net: http://minimopar.net/charging.html

 

[JG1966]

Here is one of many articles on how to test Mopar electrical systems on the net: http://minimopar.net/charging.html

Thanks Colorado. I've read that article -- and many others trying to figure this out -- and this one gets me confused. For instance, in the article it says ---- Check the voltage across the alternator output terminals (the top, large terminal is the positive and the lower, large terminal is the negative) ---- I only have one large output terminal and two field terminals.

 

[coloradodave]

Here's another: http://www.allpar.com/fix/codes/sensors/charging.html

And a video:

Good luck.

 

[JG1966]

I wanted to update everyone who helped. I noticed during testing that I had no engire to firewall ground strap. (I recently rebuilt motor and hadn't noticed there wasn't one put back on). Well, I put on strap and now car is charging like a charm. Easiest fix ever after two days of diagnostics and wracking my brain. Fortunately a new battery (which I needed anyway) and a $20 voltage regulator was the only money I threw at it. Thanks everyone.