More Hairball wiring

I've got some of the wires figured out for the hairball, but the one that's stumping me is the starter wire. I traced it out in the wiring diagram, and sure I have the right wire, but, with the key on it gives me 12 volts and when you turn the key to start, it drops to zero. It's backwards. I tried tracing it back from the clutch switch (the interlock that makes you step on the clutch to start the motor) to the relay under the hood, to the fuse block, to the wire, and they all are backwards. Very strange. Maybe it has to do with the ECU being removed?

Anyway, today I decided to stop messin' around and went to the key switch, where the voltmeter showed that the wiring worked as expected - zero volts until the starter switch was activated, and then it hit 12 volts. I used a tap to connect a new wire right of the switch and down to the Hairball. In the picture you'lll see a bright red wire going to a yellow tap. Why didn't I think of that before?