1940 LaSalle Light selection knob (rotary) under the dash

[jwaldrich]

I've looked at numerous diagrams and am unable to come up with a wiring schematic/diagram that shows the NUMBERED posts on this 4 post switch.

This is the switch that dims the lights on the dash and selects other functions as well. It is physically located under the dash by the driver's right knee.

Please look at the attached picture of the switch.

John Aldrich

[Barry M Wheeler #2189]

John, the lamp dimmer switch may be located as part of the headlamp switch. (It is on the 1941s.) The switch you pictured is possibly an aftermarket one added by a previous owner. (It looks nothing like the heater switches, etc.)

[harry s]

I agree with Barry. If the dash light rheostat is not part of the light switch then it would have been where you describe but that is the only function and the knob is smaller with serrated edge.      Harry

[Bob Schuman]

The 1940 dash light switch was not part of the headlight switch, it was mounted to the bottom edge of the dash, and looked similar to the one in your  picture. I must have dealt with the wiring when I had my 40 LaSalle dash out some years ago, but memory is not helpful about how it was wired.

[Fred Pennington 25635]

John, The Dimmer wiring is as follows:
Terminal 4 goes to Terminal 3 of the Head Light Switch
Terminal 3 goes to the Instrument Cluster and Clock lights
Terminal 2 goes to the Ignition lock cylinder light
Terminal 1 goes to the wire that runs between the Headlight switch and the clock power.
The last one seems weird but that is what the service manual shows and I confirmed it with an ohm meter.

Hope this helps

[harry s]

That's a big change from the '37 which only has two wires. Always learning.
Harry

[Brad Ipsen CLC #737]

The other function of this switch is to turn on the dash lights along with a key light without the headlight switch on.  If you try to insert the key when it is dark it is almost impossible to see the key hole due to its location.  Check the Operating Hints manual. It has 3 functions.  Dash light and lock light on at all times regardless of the head light switch.  Dash lights on with the head lights on but no lock light and dash light diming function when the headlights are on.  Nothing to do with the headlight diming.  A very interesting switch.  I had missed the lock light function for many years and had struggled with the non functioning of the lock light.  I just thought the light had burned out but in checking for a burnt out bulb I learned I just didn't know how to run the switch.

[las39]

And here is a diagram

[jwaldrich]

John, The Dimmer wiring is as follows:
Terminal 4 goes to Terminal 3 of the Head Light Switch
Terminal 3 goes to the Instrument Cluster and Clock lights
Terminal 2 goes to the Ignition lock cylinder light
Terminal 1 goes to the wire that runs between the Headlight switch and the clock power.
The last one seems weird but that is what the service manual shows and I confirmed it with an ohm meter.

Hope this helps

Thank you Thank you Thank you!!!!!

I was just on my way to wade through it again and you have simplified it tremendously.
My problem was WHERE to bring the power in from the light switch. My schematic shows power coming in from number 2 on the light switch but there is no wire on it rendering the entire schematic as questionable.

I have a service manual but what I have wasn't helpful at all. I have the 1939/1940 Manual. Wait a minute... they are SHOP manuals! Not the same I am thinking.

Again, cannot thank you enough.

[jwaldrich]

John, The Dimmer wiring is as follows:
Terminal 4 goes to Terminal 3 of the Head Light Switch
Terminal 3 goes to the Instrument Cluster and Clock lights
Terminal 2 goes to the Ignition lock cylinder light
Terminal 1 goes to the wire that runs between the Headlight switch and the clock power.
The last one seems weird but that is what the service manual shows and I confirmed it with an ohm meter.

Hope this helps

Just wanted you to know that I finished up the wiring yesterday and am pleased with the results which might not have been achieved without your help!