VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1940 wiring harness and tailgate lettering

I am installing a ynz wiring harness in my 40 pickup. My truck has a slide left and right switch that is located left of the ignition switch under the dash lip. The wiring diagram refers to it as "instrument lamp switch" I was told by Ynz that the switch has two funtions, if you slide the switch to the right and if you have the "option" you have a lighted key hole light, what is required for this option? What is the funtion of the switch when you slide it to the left? Does it just turn on your dash lights? I painted the truck cab and box factory green color, was the lettering on the tailgate left green or was it painted black? Thanks, Harold Pickett

I would suspect the function of the switch is described in the owners manual. It was used in trucks from 1940-1946. The parts book calls it an instrument panel dimmer switch. I see no mention of it in the 1940 Engineering Features or truck data book. From what I recall in one position it turned off the dash lights (or perhaps just dimmed them?)
In looking at the wiring diagram there appears to be three wire connections on the switch. The center connection is for the hot wire that is connected to the light switch. The wire connector to the left side is for the instrument lamps (either turn-off or dim?) and the connection to the right is for the ignition switch lamp. This leads me to believe that the ign. switch lamp was lit anythime the head lights were on....regardless of the position of the dimmer switch.
They used the word "option" differently than we do. I believe they meant it gave you the option of have the light off or on.
The tail gate letters were not painted . This would have cost GM money
Some one with a 1940-46 truck may give more info as to the functions of the switch.

Chevegene: Thanks for the info, I have one more question concerning that slide switch(instrument lamp switch) Ynz has a wire that they say it goes to "instrument lamp rheostat switch" and another wire that goes from the "instrument lamp rheostat switch to instrument lamps" Are they talking about the "instrument lamp switch" There is no rheostat on my 40 light switch so I assume that they are talking about the instrument lamp switch. Thanks Harold Pickett

I would recommend you call YNZ. I found them to be highly knowledgeable and willing to go the extra mile to assist their customers.

OK, I found the info.
First there is no rheostat in the 1940-46 light switch. That was a new feature for 1947 AD trucks.
The switch under the dash has THREE positions.
Way to the left lights the ingition switch,throttle and choke area, ash tray and to quote Chevrolet "provides sufficent light to enable the driver to rear addresses etc"...so its kind of a reading light
Way to the right turns on the instrument cluster lights only.
Center position turns off alll lights.

The reheostat they are talking about is actually the under dash switch and it does not contain a rheostat.

Chevgene: Again, thank you for the information. I do not see anyplace that there was a socket to install the light to operate the left side switch functions, it must have been a accessary lamp but the switch is there. Harold Pickett

Harold,

My 40 1/2 ton pickup has the "courtesy" light which illuminates the ignition switch, choke and throttle knobs, cigarette lighter and ash tray. The bulb socket mounts in a vertical bracket held in place by the choke and throttle cable thimbles behind the dash.

My wiring has been re-done, but I suspect it is set up as original. The three-position switch under the dash is powered by a lead from the headlight switch which is hot whenever the headlight switch is in the "parking lights" or "headlights" position. When the three-position switch is to the left of center and the headlight switch is on, the instrument lights are on. When the three-position switch is to the right of center and the headlight switch is on, the "courtesy" light is on. When the three-position switch is in the center position, the instrument lights and the courtesy light are off, regardless of the position of the headlight switch.

Mark Yeamans
VCCA #35724