TO20 won't charge.

DaleB · Sep 28, 2016

1949 TO20 converted to 12 volts with Ford alternator and voltage regulator long ago. Alternator is new and tested good. Tried two new regulators. It has a new battery. Checked all wires for continuity. All good. Wired as shown. Never had connection to A terminal on voltage regulator. I'm baffled as to why it's not charging anymore. Any suggestions for troubleshooting?

Alt###Reg
BAT-------------Ammeter-------Block---Cutoff Switch---Battery
#####I-----------------------Ignition Switch
#####A (no connection)
STA-----S
FLD-----F

# = space to make things line up under alternator and regulator
Please forgive the above...couldn't get picture to load.

Steve@Advance · Sep 28, 2016

Evidently there are several ways to wire those. Looked through several, you can look too, just search "Ford alternator and regulator wiring" under images.

Here are a couple, one should fit your needs.
Alternator/regulator wiring

DaleB · Sep 28, 2016

Thanks for the response. I wasn't really questioning the wiring. It's been that way for over 20 years since I have owned it except I added an ammeter a few years ago.

I did try adding a wire from the regulator A terminal to the battery + as in the second diagram you provided to see if that would help. It made no difference. Is there a way to temporarily force the alternator to charge?

Steve@Advance · Sep 28, 2016

You can test the output of the alternator by unpluging the regulator, bring the RPM up, use a jumper between the A and F terminal, (provided you have 12v on the A terminal). This will also test the wiring from the regulator to the alternator.

The alternator will go into full charge, you should hear it whine and slow the motor. But don't leave it that way! It will overcharge the battery and overheat the alternator!

DaleB · Sep 28, 2016

Sorry, I don't quite understand. What wires do I disconnect from the regulator? Just the F and S? Do I leave the I terminal connected to the switch? Do I jumper A and F at the voltage regulator. I don't have the A terminal connected now but I can wire it to the battery.
Thanks!

Steve@Advance · Sep 29, 2016

Just unplug the whole thing. That gets the regulator out of circuit.

What the jumper does is connect 12v to the F terminal of the alternator. You can do the same thing at the alternator, jump from the BAT terminal to the F terminal.

Also make sure you have 12v at the BAT terminal. If that connection is not there, the power the alternator makes will not have any where to go, so no charge.

DaleB · Sep 29, 2016

OK...I disconnected all wires from the voltage regulator, checked voltage at batt terminal of alternator and have 12.7 volts. Ran a jumper wire from batt terminal of alternator to fld terminal of alternator. Ran tractor at high rpm. No charge showing on ammeter and have 12.7 volts across the battery. This would seem to indicate a bad alternator (even though it is fairly new) so I had it checked again. Tested good several times. Also took it to another place and checked good there too. I'm at a loss. Since the batt terminal at the alternator has 12.7 volts, I assume that wiring from that terminal to the battery is good. I've checked the continuity of the wires in that circuit too and checks good. I'm at a loss...

Steve@Advance · Sep 29, 2016

Well, I'm at a loss too...

Makes no sense that it checks good but won't charge with the field jumped to battery. About all I can think of is maybe the alternator case is not grounded, but that is near impossible with it bolted to the engine.

Assuming the belt is tight, even then it should do "something".

Where you had the alternator tested, is that an auto supply or a repair shop? If it is a shop, any way to take the tractor in and let them test it, wire it, get it working?

Or another alternative, replace all of it with a one wire alternator. Eliminates everything but a single 10ga wire to the amp meter.
One Wire Motorcraft

DaleB · Sep 30, 2016

Went out this morning and tightened the alternator belt. Was hoping that might be it but didn't help.

I had the alternator checked at OReilly's and Autozone where it tested good.

I guess I'll have to load it on the trailer and have it checked on the tractor. However, I'm close to opting for the one-wire alternator.

TO20 won't charge.

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