Great! Glad you got it figured out.

 

So the glow plug harness wasn't melting the feed or switch side was melting, that makes more sense .

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thats why i said it would be a ground issue ..... the only reason it would melt wiring like that is increased load 1 or 2 bad ground and the power wire is searching for a ground source ( known as reverse polairty feedback )... its kewl how it all works ...... still wrapping my head around some electrical ....... multiplex in a 45 foor MCI ... AAAHHHH one button running 7 different things ???? what ???? goes by pulse width and electrical ohm in low volts ...... wow.... talk about confusing and hard to diag ..

 

You should check check out paul danner on youtube. The term Reverse polarity is typically used in electric motors and magnetic fields. The lack of a ground or a bad ground won't burn a wire. A short to ground will melt a wire, the loss of a ground will prevent the circuit from being completed. A short to ground could be through a component or via a wire that touching a ground source. At the point of a short to ground your wire is the weak link. Its the fuseable link where the energy escapes.
I'll pm you my email. If you need help just email me.

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