Go to pdf page 497 in the below manual.
1955-1959 Chevrolet Truck Factory Assembly Manual pdf
Main Wiring Harness Assembly and Dome Light Wire
Assembly To Lighting Switch Assembly Instruction
Section 12, Sheet 20
The manual came from
THIS PAGE and clickIing on Sticky:
55-59 Truck Assembly ManualFor some reason the thermal circuit breaker on the ribbed dome lamp wire failed to open. that in turn melted the wire.
You probably need a new switch but you have to find the short in ether the ribbed dome lamp wire or the orange stoplamp wire or both.
Otherwise you'll be in the same boat.
The ribbed dome lamp wire and the orange stoplamp wire are connected to the same thermal circuit breaker.
The orange stoplamp wire could have shorted and then back fed the short into the ribbed dome lamp wire.
That kind of reminds me of a time when I was burying telephone drops from the home to the telephone pedestals.
I got a call from the boss to come to a home where they were having phone problems.
There was a trailer home behind the home and at one time someone must of buried romex from the trailer to the home power meter
That day the renter of the home was digging a hole with a auger in the back yard to put up a clothesline pole.
The auger hit the romex and twisted the romex around the auger bit which created a short.
The thing was they connect the romex on the hot side of the meter, so there was no circuit breaker and free electricity.
They also ran the romex inside the conduit so you couldn't see it.
When the romex shorted, it melted the romex insulation which shorted out the telephone box ground which was clamped to the conduit.
The electricity also went down the telephone drop wire to the telephone pedestal and killed a bird that was sitting on top of the telephone pedestal.
Electricity is some weird stuff.
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