1985 Chrysler 5th Avenue battery - alltornator - Volt reg.

The picture is a voltage regulator, not sure if that will help?

Use a voltmeter, B+ lead to positive battery post, negative to ground. Run engine at 1200 rpms all acc off. At 80degrees ambient, reading should be around 13.9 volts. If the reading is below the limits or fluctuating, check the voltage regulator ground, it grounds through the mounting screws.

With the engine off, take the regulator connector loose, make sure the terminals look ok. Turn the key on, no crank, both the field terminals, usually green and blue wires, should show battery voltage, If this checks out, my info says to replace the regulator.

I don't have a current diagram on your charging system, the above info came from an old manual. Use the above info where applicable. I'd check wiring circuits also.

It sounds like the regulator in the alternator is bad. Check the voltagr at the battery posts with a volt meter, engine running. The meter should read between 12.5 and 14.5 volts. If it's above this range, the regulator is bad. If below this range, either the regulator, the alternator or both are bad. Hope this helps.