1979 402 Mercury ignition switch wiring

allen17

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Apr 1, 2014
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Hello, all. I'm new to the forum and have a question that hopefully someone can answer.

I need to replace a bad ignition switch. I'll be replacing it with a Sierra MP41000.
After some digging around in the forum, I came across this bit of information:

Switch..........................Engine harness
B........................red
C........................grey
S........................yell
M........................blk
M........................Salmon
I.........................white
Brown to front 3 prong connector

Instead of salmon, my harness has an orange wire. I have a wiring diagram in a service manual that shows all these wires in the controller and the engine. I have an understanding of all the wires except the orange and white wire. The white wire travels to the engine connector but does not continue inside the engine cowl. In the controller, it hooks to the switch, one side of the choke button, and one side of the tach connector. The orange wire goes through the connector to the terminal block on the engine, then to a switch box.

Can anyone explain what these wires are for?
Is orange ignition, or is the white one?
I'm not certain which to hook to the I pole on the new switch.

Any help will be greatly appreciated!
 
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