Electrical: 1950 Commander Map/Instrument Switch

[studejack12]

1950 Instrument/Map Light Switch -- I have installed a new wiring harness but the lighting is not working. (I haven't installed the battery yet, just using a battery charger to test, upon the recommendation of somebody who knows what he's talking about, unlike me). The wiring diagram does not indicate which posts on the map light switch the various wires go to. The switch has three letters: M, B, and I (which is a triple). What do these letters even stand for? I looked on the forum for advice, but all I found was information about a 51, which is a different set-up. Thank you

[StudeRich]

How many wires are there to the switch ?
You should have at least a wire to the Dome Light, one to the Map Light and a Power IN from the Fuse Panel, Circuit Breaker, Batt. terminal of the Headlight Switch, load side of the Ammeter, or Batt. Terminal of the Ignition Switch, whichever your Diagram prefers, all will work.

The only Mark that makes sense is "B" battery.
"I" could be the rear Interior Light (Dome) and "M" could be Map Light, I do not know.

You can use a Test Light to tell which Terminal does what.
I would use a real Battery because it is more dependable, a Charger puts out based on load.

[BRUCESTUDE]

The letter “I” is probably for instrument, or dash lights.

[StudeRich]

There is a Major Clue, the NAME of said Switch is: "Instrument Light and Map Light Switch" !

Makes sense but, this is a "Map" Light Switch that is usually Hot, not controlled by the Headlight Switch and should not power any other circuit, NORMALLY, but this 1950 switch must be a Multi-function dimmer AND Map Light Switch. Since you have the whole Diagram, tracing WHERE all those wires go will allow you to make sense of what they were doing.

[studejack12]

This morning I'm really appreciating the state of Washington! Thank you boys so much for helping me.

The number of wires to the switch is an interesting question. According to the diagram shown here, there are only four -- except this car is a two-door, so perhaps only the dotted line applies in the stead of the upper right "L" wire. (The diagram does not show the transmission indicator light wire, which presumably should be included. The car is automatic.)

I have included pictures showing the wiring before I took everything apart. You can see why I decided to embark on this project. The problem was, while everything WORKED beautifully, the lights, everything, it LOOKED like an arsonist's dream. I was always worried that a fire would land on my crotch one day. What I did not realize until I took everything apart was that Jerry had converted the headlights and tail lights to 12-gauge wire -- not 12-volt -- while retaining much of the old brittle wiring you see in these photographs. That is why I didn't necessarily trust the wiring of the switch shown in the photos. I have replaced much of the old wiring except for the special harnesses coming out of the flasher, including the turn signal telltale pigtails.

Any insight would be much appreciated. In case it is not apparent already, it was Jerry Kurtz's Commander Starlight coupe with D.G. auto.

[bezhawk]

Except for the two cut and taped off wires, it looks far better than average. No crumbling insulation or bare wires.

[studejack12]

There's something that bothers me about those blue crimped connections -- and there were a lot of them. But if I had to do it over again I would have left it alone . . . and just carried a fire extinguisher.

[studejack12]

Here's the switch