1961 generator output testing

[The Okay Boomer]

Hello classic T-Bird community. My 1961 (390 cu in, convertible) has a charging issue. My battery slowly drains as I drive the car. I need to charge the battery every few weeks to maintain 12.7 volts (engine off). I've installed a new battery, and a new voltage regulator, but the voltage still decreases as I drive. My battery is at 12.7 volts with the engine off. After starting the engine, it increases to 13.2 volts initially. Then it decreases to 12.5 volts after idling a few minutes. If I turn on the heater fan, it drops to 12.2 volts. I suspect the generator is bad. Can you please tell me how to test the generator output? Can it be tested with a multi-meter? Appreciate your advise. Thanks.

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[Frankie the Fink]

A generator should put out between 13.8V to 14.2V at a fast idle as measured across the battery terminals...pretty steadily.

If not there is a problem That is your test. The measurements you cite will not keep your battery charged nor your accessories properly powered (e.g. dim lights, etc)..

UNLESS you can find somebody with an "old school" growler (not many around now).

You will have to find a specialty shop to get it properly checked out.

The generator could be weak, need brushes or a fan belt could be too loose.
Did you polarize the system when you replaced the voltage regulator ? And is it a repro ?
Some of the repros are just terrible.

 

[Mrjagrock]

Some of the Parts stores (Auto Zone, Oreillys) can check your Generator output for free!

 

[Ricky R]

I had the same charging issue with my 61 recently. I eventually figured out it was the voltage regulator, but here are some things I learned along the way. First, make sure all the connections are tight at the generator, the voltage regulator and the BAT side of the solenoid switch (where the sire from the voltage regulator connects) Also make sure the drive belt is tight. You can do a basic test of generator output in the car or on a bench. Disconnect the 3 wires from the ARM, FLD and GND posts of the generator. Connect a jumper wire from the ARM to the FLD terminal. Connect a meter set to DC volts between the ARM terminal and GND terminal. If you've left the generator in the car, Start the car and see if the volt reading spikes up. It's best to have a friend help because the voltage regulator has been disconnected meaning that the volts can spiral up pretty high if it's charging. You don't want it to go above 20 so when it approaches that, have your helper turn off the ignition. You can also remove the generator and do the same test using a socket on the pully retaining nut and turning it fast with a drill. If it's not charging you may be looking at replacing the brushes or a fuller rebuild. If it is charging, move onto the voltage regulator. The VR basically tells the generator when to start and stop producing charge, and feeds the charge to the battery. You say you replaced the VR. New ones do need to be polarized. Its a simple process. Disconnect the field (FLD) wire at from it's connection on the regulator. Touch the field wire to the battery (BAT) wire at it's connection on the regulator for 2 seconds (it should arc a little bit). Do it a few times. Re-connect the field (FLD) wire to it's connection on the regulator. Start the engine and see if it's charging.