MTFCA Forum

The attached diagram appears in the 1988 MTFCA Repair and Restoration guide (p22) and in Service Bulletin Essentials (p143).
However, the two starters I have worked on are different. The two short connecting wires are actually joined to each other, and are located opposite the main terminal. If I were to connect these field coils as shown, there would be a lot of heat, but no magnetism! My starters have their two 'left' fields coils connected in series from the input to the tails, and the two 'right' coils the same. The tails then connect to the insulated brushes, and the other pair of brushes then go to earth (ground).

Is this correct?

Are there different designs around, or is this diagram wrong?

This is from a post that admin jeff posted. It sounds like your starter has been converted to 12v!

Stock they are wired in parallel. The 12v conversion wires them in series. Using the equation P=VI,(power equals volts times current) you get half the current when you do that. Thus, when wired in series you essentially get the same stress on all components as if running 6v. This sounds easy, but as I've discovered doing a few of these conversions now, it's a royal pain in the a$$. A LARGE soldering iron, big wire, good insulators, silver based solder and oodles of patience are all necessary to do it right. You also have to get the polarity/magnetism of the poles right on each field coil or nothing works.

Here is the link to the posting:
www.mtfca.com/phpBB3/viewtopic.php?f=2& ... ngs#p76257

Hope this helps!

The starter wiring diagram might represent a 12 volt co version. Others may have other ideas

Art Mirtes

Richard is faster than. I am

Not easy to do the polarity must be maintained

If you look at picture you posted it say to connect one wire to the 3rd brush. Believe you have wrong diagram.

My thanks to Richard - a very interesting link.
However, the material there seems to confirm what I still suspect. Which is that the diagram I posted is not correct, at least for some starters.
Neither of mine has been converted for 12v. The field coils are connected as two pairs in parallel, not 4 in series.
Note that the diagram has a reference to a 'third brush'. That would suggest it's a generator.

Chris
If you look closely you will see the diagram you posted is actually for a Model T generator field winding N/S pole orientation.
Someone apparently used a Generator diagram and captioned it "Starter"??
Ron Patterson

That diagram appears in the mtfca Electrical System guide with the caption "Testing Starter Field Coils"(pg 22, 2008 edition). Either a typo in the original Ford service handbook or Henry simply being frugal and repurposing things.

UNDER NO CIRCUMSTANCES SHOULD YOU CONNECT A BATTERY TO STARTER PIGTAILS AS DEPICTED IN THE DIAGRAM! ABOVE! The would be the equivalent of shorting the battery terminals together with a crowbar and COULD BE DANGEROUS TO YOUR HEALTH!
The diagram above is CORRECT for connecting a battery to a GENERATOR field winding to verify the windings magnetic N/S orientation with a compass as shown
There was a period of time when the sole manufacturer of Model T generator field windings was incorrectly assembling the field windings in the wrong sequence. The were the correct number of N and S windings but they were assembled N-S-S-N or S-N-N-S.
I found it was always best to check each winding assembly to ensure they were correctly assembled N-S-N-S orientation using the test in this diagram before installing them inside the case with the pole shoes/screws before final assembly.
The starter pole windings must be jumbled up (there are several methods) for a to get the full series circuit (as opposed to original series/parallel field circuit) that is best for the 12 volt conversion.
One other comment at the risk of criticism; I found the MTFCA Electrical Manual severely lacking in providing complete and necessary information that one needs to properly rebuild Model T Ford generators and starters. Using them is a trap for logical folks, by that i mean it looks just a little too easy and the real troubles lie in the details not provided.
Someone needs to take the time to rewrite the MTFCA Electrical Manual.

"Someone needs to take the time to rewrite the MTFCA Electrical Manual."

Preferably someone like you, Ron, who has the knowledge, patience, and writing skills to convey the information. Several other MTFCA manuals would be vastly improved by a similar rewrite. jmho, jb

jab35 wrote: ↑

Sun Nov 27, 2022 11:55 am

"Someone needs to take the time to rewrite the MTFCA Electrical Manual."

Preferably someone like you, Ron, who has the knowledge, patience, and writing skills to convey the information. Several other MTFCA manuals would be vastly improved by a similar rewrite. jmho, jb

And newer photos as well.

I'm pleased to have my suspicions confirmed.
Thank you Ron, and others.
Although the error is in the MTFCA publication, the diagram was also the Ford Service Bulletin of March 1st 1920!
That bulletin covers both starter and generator but if you read it carefully, it is clear that they are describing a generator test with that diagram.

Chris

I just refered to the Service Bulletin that you referenced. Reread all prior to the diagram, and it is refering to the generator, not the starter

Service Bulletin: March 1920, pages 174 (testing the yoke for shorts with a lamp, and page 179 (with the diagram)

I do not know if the MTFCA Electrical Book is correct or not, but the Service Bulletin is not in any way in error. Take another look...

text below for those who do not have access to the Service Bulletin(s). I have Bolded key information, not to shout but to bring attention as to what is being referenced by what...

452. Care should be taken that the leads
on the generator yoke are connected to the
proper brush terminals. The earlier fields were
wound opposite to the later, and it is therefore necessary to cross the leads on the latter.
To determine how they should be connected,
test the field with a battery and compass as
follows:

453. Attach the leads to wires leading to
the battery and try the field poles with a compass as shown in Fig. 259. The north pole
(blue) of the needle will point to one pole, the
south to the next, etc. If the poles do not
indicate with reference to the terminals as
shown in the diagram, reverse the leads on
the battery wires and test with the compass
again. If it indicates properly now, the lead
attached to the Positive ( +) wire from the
battery is the one to be attached to the third
brush.
454. It is impossible to mix the leads on
the motor, as both are secured to the positive
brushes.
The Brush End Bracket
455. The brush end bracket of the starter
motor differs from the generator bracket, in
that there is no oil hole in the bearing end,
the bearing being of the self-lubricating type,
and a press fit in the bracket.

and then your diagram (259) is printed