Question About Interior Cab Light - 1959 GMC

[DA68]

Can anyone tell me what activates this light? I don't see a door switch, so I'm guessing it is turned on by the headlight switch. Any help is appreciated.

[OrrieG]

You are correct. The wire to the lamp is a ground back to the switch. You can add a relay and door switches to get it to work automatically, that is what I did.

[my56chevytruck]

Originally Posted by DA68

Can anyone tell me what activates this light? I don't see a door switch, so I'm guessing it is turned on by the headlight switch. Any help is appreciated.

What i did to my interior light was to run a ground to the body and the other to a toggle switch mounted under the dash. Of course you have to run power to it. its not automatic but then I know where the switch is. I did this to eliminate wiring to contact buttons in the door jam. just another way is all.

[_Ogre]

the dome light in most gm precomputer vehicles has 12v+ to the bulb and grounds thru the headlight switch
cars also ground thru door pins, while our trucks don't have door pins the switch is designed for grounded dome light

this is the task force headlight switch



old trucks had pretty basic wiring, base truck had no fuse panel, no radio, no heater and vacuum wipers
all lighting on the truck was protected by the headlight switch, the small fuse is for instrument panel lights
the rest of the lights are protected by bimetal strips you see on the headlight switch picture
when they had an overload the bimetal would heat up up breaking the points, cool and restore power
this prevented total loss of headlights while driving, the headlights will flash

if the truck was ordered with a heater it will have an inline fuse
as accessories were added: radio and electric wipers, gm added a 4 fuse panel behind the headlight switch

[DA68]

Great info. Thank you all!