Wiring at the Terminal Box

[mmindling]

Hi, this is Martin in Ohio. Looked into the wiring on my vehicle today to correct some mistaken color codes.

However, found more questions than corrections:

*In the Model A Ford Mechanics Handbook by Les Andrews, shows the
Black wire from the coil connecting with the Yellow/Black Tracer wires
on the driver's side terminal of the box. This would then be routed
by the Yellow/Black Tracer to the Ampmeter charge side and to the
generator cut out. The instructions here seem to
be helpful because they identify "drivers" or "passengers" side.

*In the original Ford service bulletins, the Black wire goes to the
terminal with the Yellow wire connections ( Fig 444). This would
be routed to the Ampmeter discharge post and the Starter Motor
terminal. No mention of drivers or passengers side.

Also, my coil is a slant pole and does not indicate which side is positive
and which is negative (drivers or passengers side would be really helpful
here). Les Andrews says the red wire from the ignition switch should to
to the positive coil post. Therefore, the black wire should go from the
negative coil post to the Ampmeter / Generator terminal post which
would be Yellow / Black Tracer??

Can anyone shed some light on this wiring contradiction? I have
thoroughly confused myself. But the two diagrams are clearly different.

Regards,

Martin Mindling [email protected]

[Roadster62]

Good luck, proves my point about electrical things, no two people can give the same answer to a question.

[Jim/GA]

Either wiring will work. The only difference is that one will make the ammeter needle twitch a little bit when you turn the key on and crank the engine (because the power going to the coil from the battery has to go through the ammeter). The other will not make the needle move because the current is taken from the battery before the ammeter.

I like having the ammeter needle move a little bit when I turn the key on and crank. It confirms that the points are working. To do that, take the power feed for the coil on the generator side of the ammeter, not the battery side.

I don't know how to pick the + and - sides of a slant post coil. Sorry.

[marc hildebrant]

If you read the service bulletins you will see that a change was made to the ignition circuit to pick up it's power after the amp meter.

I have no idea why the original design had the ignition circuit not flow through the amp meter.

Marc

[Tom Wesenberg]

About the same time Ford switched sides for the feed wire, they switched coils from slant pole to straight pole. To add to the confusion Ford switched polarity on the coil posts when they switched the wiring to run the coil through the ammeter. However, a few slant pole coils were made with the polarity the same as the new straight pole coils. So, on ALMOST all slant pole coils, the driver's side is the red wire, which leads to the switch, then points, and is the POSITIVE side.

See page 390 in the Service Bulletins. If you have any questions about coil polarity, check out what is posted by the Chicagoland MG club:

http://www.chicagolandmgclub.com/tec...neral/574.html

I did the same as Jim and moved my slant pole feed wire to the other terminal, so the drain would show on the ammeter. Now while the generator is charging, the ammeter shows ONLY the amps going into the battery, where the original way it showed the amps going into the battery, plus the amp or so to run the slant pole coil.

[Drive Shaft Dave]

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It would seem to me having the ignition running through the ammeter, if the ammeter went open circuit, the engine would die thus saving the generator from going to high voltage. Does this make sense?

[Tom Wesenberg]

Originally Posted by Drive Shaft Dave

It would seem to me having the ignition running through the ammeter, if the ammeter went open circuit, the engine would die thus saving the generator from going to high voltage. Does this make sense?

Actually the car would keep running because it has generator power on one side of the ammeter and battery power on the other side.

[Drive Shaft Dave]

Thanks for the reply Tom.

[H. L. Chauvin]

Also, after the latest specified Model A Ford wiring changes, it was recommended to connect all additional Model A electrical items to the Driver's Side Terminal of the fire wall terminal box; however, "if" one obtains & installs "Logo Lite" turn signals, the Logo Lite manufacturer recommends connecting their Logo Lites to the Passenger Side Terminal of the fire wall terminal box.

[Marco Tahtaras]

If you look closely at the Service Bulletin on the wiring change you will see that with the slant poll coil you need to crisscross the black wire from one side of the coil to the opposite side of the terminal box. This changes it for the ignition to read through the ammeter while retaining proper polarity of the slant pole coil.