40 Merc under-dash switches

[Clem Clement]

DR,
You are correct.
Clem

[Clem Clement]

Suggestions, please on how to test this system to determine which way the switch is on. The switch moved front -to-back. The mounting plate is held on by 2 slotted screws. I can't see/feel the other end of the screws. Wire end is hard to reach.

I haven't studied the dissy connection end.

[rotorwrench]

Integral would have the meaning that is is all part of one assembly like the later cars in the 8BA era.

A lot of the old rheostats were actually built pretty well but they do wear out over time. The brush that has light spring pressure, rotates with the turning knob and has contact to the outer circular resistor ring. Usually either the brush wears out, the brush spring breaks, or the circular resistor gets worn though at some point on its circumference by the brush. I've seen reproduction replacements for the 42 through 48 type but I haven't seen the earlier ones so much. They are likely available from some source though. How well they are made is the big question. The dark blue knobs were used on 1940 Mercury so that would likely be the difference from a dimmer on a 1940 Ford Deluxe.

The rheostat would only need connections for one end of the circular resistor and at the rotating brush for variable power drop. Some rheostats have an off position at one end that isolates the resistor from the brush.

You may have to isolate that flip switch to test it to see what setting is ON. If you have a volt meter and the switch is connected, you can attach or probe at the connection to the ballast resistor or what ever it's connected to and see if the voltage changes when you flip the switch but that won't help if you have no access to terminal ends at either the origin or termination of that switch circuit. Spot lights generally always have their own switch near the control handle. Driving lights or some other accessory may have been wired in. It's just hard to tell on our end how to go about helping with this. A person would have to follow the switch circuit wiring to its end termination.

[Clem Clement]

I put a light bulb on the dissy nut and the light did not change brightness with the moving of the paddle switch. (The ign. was on but the car not running.)

[tubman]

Turn the engine over a couple of times. The points may have been open when you tested it.

[Clem Clement]

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I'm more confused. I took the power source from the top of the coil at the knurled nut. I have a grounded light bulb . Either position of the paddle switch and the bulb illumination was low. Going to the battery for both power and ground and the bulb was much brighter.

This Afternoon I looked again at the wires under the dash.( I have the top 3 of my neck vertebra fused so I don't twist very well. To my amazement there is a small pill-like shape which I think is a resistor in the line to the paddle switch. The "pill" has white alfa numeric markings on it.

In my mind the purpose of the bypass is to bring 6 volts to the starting system?

[Clem Clement]

Big discovery!!
With a camping mirror and a better light, I could see the switch. The switch has a collar with on/off tab attached!!! Off is forward. When I get to start the car I will study more.

[slowforty]

My switch started to act up. I by passed the switch and dash light are much brighter now.
and I dont drive too much at night anyway