Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

I’ve been troubleshooting multiple issues with lights & horn on my December 1928 Model A.
Traced them all back to the Rotary Plate on the steering column. Original Rotary, new wires soldered to it 50-60 years ago (we got the car when I was a kid!).

Here are a couple helpful threads I came across:


From 2013:
fordbarn.com/forum/showthread.php?t=122368

From 2016:
fordbarn.com/forum/showthread.php?t=196142


Along the way I scrounged my dad’s old parts bin from the 1970s and found a Mystery Rotary Plate.
I’m wondering if anybody here has ever seen this.

As you may know there’s 2 basic Rotary Plates for the Model A as shown in all the Books:
1. Thru Feb 1929: Rotary Plate has 4 contacts (plus horn in center). Brass Ring that rotates from the steering wheel switch has 4 contacts that connect them. 2 Lighting Positions: Goes left for brights, right for dims.
2. Two variants: Both have 3 Lighting Positions, all same direction on the switch.
a. 2a: Feb 1929 on: Rotary Plate has 9 contacts (plus horn in center). Brass Ring has 3 contacts to connect them. 3 Lighting Positions: Parking, Bright, Dim.
b. 2b: Feb 1929 on: Rotary Plate has 9 contacts (plus horn in center). Brass Ring has 3 contacts to connect them. 3 Lighting Positions: Cowl, Bright, Dim.

Naturally there were no 1928 Rotary Plates in the 60 year old parts bin, they were all 1929-1931 style with one exception.
3. Unknown Years: Rotary Plate has 6 contacts (plus horn in center). Brass Ring has 3 contacts, 1929-31 style. 2 Lighting positions, Goes left and also right, 1928 style.
Anybody ever see a switch like this?

I’ll try to include pictures of the Rotary. The “clock” I’m using is viewed from the drivers seat.
Wires are too old and dirty/faded to read colors. If I really use my imagination I can see a Yellow+Black tracer wire at Noon, seems thicker than the others (hot from generator?), cant read any other colors.

Pictures from the back (wiring side)
Noon-3oclock
3-6oclock
6-9oclock
9-12oclock
And a picture showing the Rotary, 6 contacts and 3 “off” contact dents, and the Brass Ring with 3 contacts.
(Edit ok I added the pictures)

Any ideas on what car this Mystery Rotary Plate is from?

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Giving this a bump cuz I was just able to add the pictures.
Hope they help.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Ford used the steering wheel switches up through 1939 so there are likely other variations. The MAFCA electrical PDF document shows the ones used in the model A era.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Good suggsetion. I looked here, this has all the diagrams for 1932-40s, 1932-39 has the rotary switch but they all look like the 9+1 contact 1929-31 style, vs
4+1 contacts 1928
6+1 contacts Mystery Rotary
9+1 contacts 1932-39

I wonder about the Model T or Brand X?

Link for 1932-up Diagrams:

http://www.vanpeltsales.com/FH_web/f...electrical.htm

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

I don't think it's for a Model A. I've never seen one with a tab
like this one has.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Me neither. And yet, the forward stamped steel cap snaps right on there just as if it was a Model A part.

Maybe it's a very early 1928 Mustang switch LOL.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Could be plate the for 28 with cowl lights.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

I wondered that too. Dont see many 28s with cowl lights, I never used to keep track but dont remember any.

Section 18 in Judging Standards shows Cowl Lights Oct 28 to Feb 29, BEFORE the Twolight setup came out. After that they'd be wired Twolight style of course like the well known diagrams with the 9+1 contact Rotary Plate.

But what about Cowl Lights BEFORE Feb 29? What Rotary Plate did they have & how was it wired?

I never thought about it.
What 28s could you even get Cowl Lights on?

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

This link shows all the different model A types on page 37. The photos above don't include a side view of the mounting base and the switch fit together as an assembly so it's harder to get an idea of it's origin. Ford may not have been the only company to use this concept and there is little available information about the components used in the Lincoln cars of that era.
https://www.mafca.com/downloads/Semi...ex%20Janke.pdf

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

I have a reproduction wiring harness for cowl lights on a September '28 Blindback that I purchased from Little Dearborn around 2000. Light switch to the left is cowl lights, to the right is headlights. The headlights themselves only have the one bulb. The brackets for the cowl lights inside the car were correct for the lights. I added the cowl lights, and was surprised to find everything ready for them on the vehicle except for the wiring harness.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Thanks thats a helpful PDF, though it shows only the 1928 (4+1) contact Rotary and the 1929-31 (9+1) contact Rotary.

Here are pics of the Mystery (6+1) contact Rotary from the side, a 9-o-clock view as in the PDF, and a 12-o-clock view showing the slot in the top of the housing not in the other housings. This is all the exact same size as the known Model A units. The lower steel bell is identical AFAIK, and the only difference I can see in the upper steel bell is the keyway slot at 12-o-clock.

Re: Light Switch Rotary Plates: 1928, 29-31, and a Mystery Plate:
 

Do your headlights have 2 filaments like the normal 1928s or just one each?