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Currently replacing old wiring under the dash of my 1940 super 8. Rewired both the dimmer and ignition switches. Both worked properly before and after rewiring. When testing both switches after removing old and before installing new wire continuity readings didn't make sense to me! The Ignition switch with key in the OFF position the multimeter showed zero resistance between the input and output wiring lugs.Turning the key to the ON position also showed,, as expected, zero resistance. How can a switch test closed and not continuously be passing current? The dimmer switch would only show continuity between the power input and the lug that didn't have the hi beem wire attached to it. After pressing dimmer switch couldn't get continuity between any of the 3 wire lugs? Does this make sense to any one?

Hello, Bill,
Assuming your 40 has a similar, if not exact components of my 39 Six, the operation is as follows:

Ignition switch: there are essentially 4 connections of the switch:

One 'hot' input, the negative 6volt supply from the battery at the starter solenoid input post.

One ground input, which is the case and mounting bracket of the switch itself.

Two switched outputs that, when the key is ON, supply -6v to 1: the jacketed cable to the ignition coil and 2: the other electrical loads such as heater, fan, etc. When the key is turned OFF, the switch disconnects the battery from the two outlets and instead connects them (both, I think) to ground. This is a theft deterrent function intended to prevent starting/running of the vehicle, unless the thief fully removes all connections to the ignition switch.

So, if you recheck the switch for continuity and isolation among the switch inputs and outputs, the above should show true.

Dimmer switch: there are three connections to this switch:

One input that comes from the light switch and is hot when the switch is in either the City or Country (2nd or 3rd) ON positions.
Two mutually exclusive outputs: one for high beam and the other for low beam.

Think of this as a switch with two possible states: the low beam output is connected to the input hot power or the high beam is connected to the input hot power. Pressing on the dimmer switches back and forth between the two.

Hope this helps,
Pat

Pat, thanks for the feed back. Your info regarding the grounding of the outputs on the ignition switch with the key in the OFF position was something I didn't know. Will retest and see if I can make sense of continuity readings. I understand the dimmer to be a single throw double pole switch, ie either the high beam or low beam terminal is hot when ever the light switch is all the way out. In my car, power only goes to the parking and dash lights when the main switch is half way out. As the dimmer switch functions properly my continuity reading will, I guess, just remain a mystery to me.
Thanks, Bill