Alternator or battery???

To continue last post.........

Make sure you run it fast enough. Make sure battery is not severely discharged. If warm running voltage is again "that low" (well below 13.5) then make these checks...........

Assuming? you have the factory Mopar type setup?

Turn key to run, engine off. Unhook the GREEN field wire at the alternator. You should see a small spark in subdued lighting. Take a clip lead and ground that alternator terminal. Not the wire, the alternator field

Now start and run the car, monitoring battery voltage. Slowly bring up RPM. It should easily pass 14, try to keep it below 16. IF NOT............

Move your voltmeter to the alternator output stud. Recheck. If voltage remains quite low, it is not charging. If the voltage at the stud is quite high, way over 16, you have an open connection between the battery and the alternator output stud.

If voltage at the output stud is low, take a second clip lead, hook to a battery source such as the starter relay big stud. DO NOT use the alternator stud. Unhook the second field wire, the blue, and hook the other end of the clip lead there. So..........

You have one clip lead from battery to one field

You still have the second clip lead grounding the second field terminal.

Repeat the run test. if output is still low in voltage, something is wrong in the alternator.

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IF the voltage "came up" in the first run test, but will not charge up to voltage when hooked up "normal," This might be in the field circuit.

Hook everything up "normal." Turn key to run, engine stopped. Measure voltage at the blue field terminal WITH the wires all hooked up. Should get close to battery

Take your clip lead, unhook the BLUE field wire, and ground that alternator field terminal

Unhook the VR connector. Inspect for corrosion. Work in and out feel for "tight." Next, devise a way to jumper across the two connector terminals. Monitor battery voltage and once again run the engine "up." IF it charges and voltage rises up above 14, .......then........

REMOUNT the VR making sure you scrap the VR and firewall clean and use star lock washers. Wiggle the connector. Re--test

If it still won't charge hooked up normal, replace the VR. Buy a good one.