Alternator wiring

I traced the blue and green wire from regulator and found the missing wires! It was hanging down behind the motor. This is what I found, I see the black wire for battery and blue and green wire for fields, but what the heck is the brown wire for? (The wire I'm holding) is that the temp sender wire 67dart273 mentioned?

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That one in your hand is the Temp Sending wire and is/was Violet.