Technical 39 Chevy light switch

My 39 Chevy light switch keeps blowing 30 amp glass fuse thats attached attached to the back of switch...can anyone tell me how to get switch out or off the dash.and does replacement fuse have to be 6volt..as that is what is in it

 

is the wiring original?Usually when a fuse blows, it's because a wire shorted somewhere in the car.

Should be a button on the light switch that lets you pull the knob all the way out. First disconnect the battery, then pull the knob out enough to turn on the headlights. then push the button, as you gently pull the knob out the rest of the way.

the button is circled, it might or might not look exactly like this. It's a generic internet picture.



After you get the knob out, you need to unscrew the nut that the knob shaft goes through. I don't remember what they look like, it's been a long time since I had a 39, but usually a large screwdriver might fit the slot.

 

Jim nailed it there, it isn't the fuse that is blowing the switch it is the shorted wire between the switch and one of the lights.
I'd pop the switch out, disconnect the headlight wire or the taillight wire (one at a time) and turn the switch on and see what happens and you may have to drive it a ways and switch wires around to figure out which circuit is shorting out then you have to find out where.

 

The replacement fuse seems a little high in value- unless it was one of those "1 fuse does everything" type set-ups- I seem to remember that was how my '37 was originally wired. The fuse doesn't know or care about the voltage, as long as the current rating is suitable.

 

the current rating needs to be suitable for the wires....because the fuse's job is to protect the wires from getting too hot when there's a short circuit, and the wires want to melt. So match the fuse size, to the wire size. If it has little 16 gauge wires, then a 30 amp fuse is way too high current.

 

Once you pull the knob out it's just a flat blade screwdriver, or a coin in the slot to unscrew the bezel nut and allow the switch to be dropped down. To figure out where the issue is you'll need to check resistance to ground to the headlights and taillights to see if anything shows a direct short, no resistance.

 

With some of the old switches you can open it up and clean/inspect the condition of things inside.