TO 20 old 12 volt conversion

DaleB · Mar 10, 2015

TO 20 has old 12 volt conversion. Ammeter indicates it is not charging. I need to verify wiring from the alternator to the voltage regulator. 3 wires from the alternator: from Bat (red terminal) to Ammeter (green wire), from FLD (white terminal) to S on voltage regulator (yellow wire), from STA (black terminal) to A on voltage regulator (white wire). Wire from I terminal on voltage regulator to ignition switch. There is also an F terminal on the voltage regulator to which nothing is connected (it is rusty looking).
My concern is whether the A and S terminals are correctly connected to the alternator (they got bumped and disconnected and could be switched or moved).

Steve@Advance · Mar 10, 2015

http://i737.photobucket.com/albums/xx11/lj6798/fo
rd01.gif

I think you have an old Autolite alternator. This
is how it should wire. The F terminal is
necessary for it to charge. If it hasn't been
connected,it could not have worked.

If correcting the wiring doesn't fix it, I would
go for a Delco 10-SI internal regulated
alternator. Much cleaner, easy wire, cheap and
plentiful.

http://www.expeditionlandrover.info/LR.images/Del
coWiring.jpg

Steve@Advance · Mar 10, 2015

Well, try this one...

http://www.clubcobra.com/photopost/data/500/img098.jpg

DaleB · Mar 10, 2015

It does have a Motorcraft alternator and the second
diagram has the same terminals. The system was
charging until a wire came out of its plug in
terminal. When I removed the piece still plugged
into the voltage regulator, the other wire was
accidently knocked off. I am sure there were only 3
wires originally going to the regulator so one
terminal wasn't being used. The I terminal never was
off. Since the bottom f terminal looks unused (rusty)
and the other two looked used (A and S), I thought
that was where the wires were supposed to go. It was
working without one of the terminals being connected
to anything. Maybe it works without the A terminal
connected and I need to move the other wires both
down a notch but I didn't think the f was used
because it is rusty.

Steve@Advance · Mar 11, 2015

Try it without the A terminal. The F terminal is the field terminal. That is how the voltage is regulated, the regulator applies power to the field to tell it to charge. As the battery builds, that voltage is reduced to prevent over charging.

DaleB · Mar 11, 2015

Back in business and charging again. Had to replace the alternator. S to STA and F to FLD. No connection at all to the A terminal on the voltage regulator. No extra wires hanging around anywhere so I think that is the way it was. Will leaving nothing connected there result in any damage? I'm not sure what that terminal is supposed to do. Thanks!

Steve@Advance · Mar 11, 2015

As long as it's charging, and not over charging, and not draining the battery when stopped, and not feeding back power to the coil so it won't shut off, everything will be fine.

Been a while, but when used without a charge light, the I terminal is not used. If the A terminal were used, it would go to the accessory side of the ignition switch, but unless the switch has been changed, there would not be an accessory terminal. So either there is a charge light, or someone wired in a resistor or diode in the circuit between the ign switch and the I terminal.

Bottom line, if it works, it's fixed!

DaleB · Mar 12, 2015

This tractor has an ammeter but no charge light. It also has a kill switch on the pos battery cable in addition to the ignition switch which is 3 position. I'll use it like it is for now anyway.

TO 20 old 12 volt conversion

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