Model T Wiring: I Learned a Thing!

[Jerry VanOoteghem]

No matter how long we do this, there's always something new to learn. I have been around Model T's my whole life, but I don't believe I've ever installed a wiring harness. If I did, it was long enough ago to have forgotten some stuff...

Anyway, this will be well known and basic to many, but what I learned is that the wiring harness for my '25 T, identified in the catalogs as "Lighting Wire Harness", in fact, only wires the left headlight, (I see the 26/27 harness does both). Since I shamefully use a distributor, I figured I don't need to buy a "Commutator Wiring Harness". Surprise! The commutator harness also wires up the right headlight and the generator.

Again, most of you already know this, but maybe some newbies, (like me, even after 50+ years of playing around Model T's), might find this useful to know. When do we stop being "newbies"?

BTW, the Snyder's Catalog is more descriptive of these harnesses than some of the other suppliers. Thanks for that Snyders!

[TXGOAT2]

But..... they're all the same!!!

[Original Smith]

This will not come as a surprise to some of you, but I got a reproduction harnesses from Langs quite a long time ago, and was unhappy. For most restorers they are ok, but not me. I had a local harness maker copy ORIGINAL harnesses exactly, and they even wove in the Ford tags!

[TRDxB2]

They are not all the same...


COMMUTATOR WIRES
The 4 wire likely are different in length
The 5 wire are for non starter cars
The 7 wire for starter cars up through 1925
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HEADLIGHT WIRING
Wiring diagrams are the best way to explain the differences. Magneto bulbs are wired in series while 2 contact filament & LED are wired in parallel.
Note that the single wire descriptions
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Ultimately the electrical components dictate the wiring diagram
For example the wiring diagram for a distributor

[Jerry VanOoteghem]

Frank,

That is exactly the wiring diagram that I used. Useful as it is, it does not state what P/N harness does what.

[Jerry VanOoteghem]

But..... they're all the same!!!

Pat,

You really need to work on letting people know when you're being facetious or literal.

[TXGOAT2]

All the same... all black.... my Grandpa had one!!!

[Allan]

The repop wiring looms I have bought recently have improved a bit. The under dash to terminal block loom now comes in something more like the correct length, but both the lighting looms still have way too long twin wires to the headlamp sockets. If I cut them back to length, the loom cover is prone to fraying, so I leave them long and wind them to the socket in a devious route. I suppose being too long is better than the alternative, but it should not be difficult to correct.

Allan from down under.

[TRDxB2]

Frank,

That is exactly the wiring diagram that I used. Useful as it is, it does not state what P/N harness does what.

The supplier descriptions of a harnesses identifies its intended use. Wiring diagrams are somewhat generic just indicating connections & not wire length etc . For example: The two Texas T wiring diagrams (1922-25 & 1926-27) for the distributor are identical except for the addition of the tail light wiring.

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However the harness for these years are routed differently. Thee diagrams reference the "factory part" number so you need to use the cross reference to match the order/supplier number. If you get confused looking at these diagrams don't worry, you wouldn't be the first. I don't guarantee their correctness.
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The lighting harness' for 1919-25 & 1926-27 are routed differently. So you could use a 1926-27 lighting harness since you don't have a commutator
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Cross reference
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[varmint]

It was easy for me to get the correct wiring harnesses for the '26 because it didn't have wires. So, I bought all of them, even the single wire harness. I don't know who made the reproductions I have but I'm happy with every last wire. The headlight wires are too long but I'll merely cut them when the time comes.

What is really missing, is some sort of buying guide per related parts, as Jerry the O.P. alludes to, to know when you have all the wires needed. Yes, the T books have a complete wiring diagram, but not so much in the online buying presence. This is not just an issue with wires, but any function. I find myself going back to the vendors to buy more because I didn't even know this other "thing" existed and have to pay shipping again. Items are presented in a list format, sometimes a related list as well.

What if there was a diagram (picture worth a thousand words)? Example: a sketch of photo of a starter, with lines extending from the starter to all the part numbers for sale, even those on back order. It might even convince me that I need to get screws for the Bendix cover. Maybe I'm just spoiled in the computer tech industry when I can see an exploded view of a laser printer with all the parts labeled. The printers will change, but the T will not. So, creating such a view should be a one time endeavor.

[TRDxB2]

There are many line drawings available via the Forum site. This is a direct link app.php/gallery/album/11
Once on the site click on the title in on of the boxes to drill down to the desired diagram

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Then there's Ecklers catalog https://turn5.scene7.com/s7viewers/html ... /Model%20T

[John Codman]

This will not come as a surprise to some of you, but I got a reproduction harnesses from Langs quite a long time ago, and was unhappy. For most restorers they are ok, but not me. I had a local harness maker copy ORIGINAL harnesses exactly, and they even wove in the Ford tags!

I bought a complete wiring set from Lang's in June 2015 and they were perfect.

[Jerry VanOoteghem]

The wiriing I bought was from Lang's as well. I was very happy with it.

[Original Smith]

I learned something this morning I was not aware of, and I've been at it for over 60 years myself. Ford used steel wire in his looms!

[varmint]

My condolences Larry. Now you have to replace all your wiring harnesses.

[Allan]

July 17 is a long way from April !!
Allan from down under.