Car stopped charging battery a few weeks ago, I have also had an ignition problem which I wonder if it's related. The car (71 Challenger w/383) isn't charging. Battery voltage running is the battery voltage as it drops, low 12s now. to fix this problem I have replaced the alternator, voltage reg twice and the battery. The grounds are good, what could it be. I looked at wiring diagram in shop manual and the troubleshooting tips. I don't have a carbon pile rheostat whatever that is, but was wondering if anyone knows how I can check if alternator is working and then trace to the problem from there. It appears like the charge gauge in the dash is an ammeter instead of a voltmeter. did Mopar really run all that current into the dash? Could my problem be under the dash somewhere?

I had to replace my defective ammeter in my 70 cuda 30 years ago. It is a good idea to bypass that thing. There were many posts on here on how to do that correctly.

It sounds like you have a multimeter so you've been able to verify that you're actually not charging? You can take that meter and make checks along the charge circuit. I'd have a look at your bulkhead connector to see if anything looks burnt or corroded in there along with the ammeter.

The alternator output originally follows a complicated path, refer to your wiring diagram. It goes through the bulkhead to the ammeter and back TWICE, as well as the switched ignition feed coming back from the ignition switch, which feed power to the ignition AND THE REGULATOR. That's at least THREE therminals in the bulkhead connector that can give trouble, on top of the alternator. To add insult to injury, many/ all? Mopars have an internal splice or two IN THE HARNESS of which I've found problems "back when" on more than three cars.

Run the car, simulate "medium cruise" with accessories off

Put a voltmeter on the battery, note the reading, and then put the meter on the output stud of the alternator. If the reading is very high at that point, you have a problem in the above mentioned circuit path, IE, wiring from the alternator/ bulkhead/ ammeter/ bulkhead/ back/ to the battery

If the voltage is low at both points, say, below 13, it is not charging. ID the blue wire to the field, check that it has battery voltage to ground. Disconnect the OTHER wire from the field terminals and ground the exposed terminal. The voltage at the alternator/ battery should immediately go up "full output" charge.

If so, you have a problem in the regulator circuit, either the regulator is not getting ignition voltage or the green wire is broke, bad, ungrounded regulator

If it doesn't charge, you have a bad alternator or you made a mistake earlier.


Additionally, you can run a temporary jumper DIRECTLY from the alternator output stud to the battery, make up with no 10 or larger. If this "fixes" the problem, you definately have troubles in the bulkhead/ ammeter circuit somewhere.

Google up the "Mad Electrical" ammeter bypass circuit.

thank you very much guys! I just ran some additional tests and I am getting 12V on the alternator field blue wire when switch is on and the alternator is putting out 36 volts between it's black wire and ground. I guess I have a wiring problem in the harness, or dash or ammeter.

You can just move one of the wires on the ammeter to the other post and make the bypass easily. It doesn't address the other issues with the bulkhead but will quickly get that gauge out of the mix.

I wanted to put closure on this and thanks. It was the bulkhead connector. I replaced the whole dash wiring harness and used the bypass you referenced. (bypassed the ammeter and drilled through the firewall connectors and soldered directly. Battery is charging again, I'm installing a Sunpro battery gauge instead of an Ammeter soon. Thanks for everything! this forum is great.

Glad yor fixed.Its a common thing bulkhead wiring issues .I follow this
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If you dont have 12 volts battery power at the positive + bolt on alternator connection.Its not going work And you need to findout why theres no power.Also if you have no key on power to alt field .You got a wire or wiring harness issue.On the engine compartment wiring harness.And need to trace it of the wiring diagram
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