That diagram is for a pre AD truck and I think that the truck in question is a 46? That light switch and wiring is definitely different than the AD. I was surprised to see that the ignition feed and the gas gauge feed are unprotected. All the cab interior lighting appears to be protected by a fuse in the light switch. I don't believe that the light switch has the bi metallic breaker.
I see that the diagram has that crazy polarity reversing switch. I think that the diagram must be older than 1946.
