I disconnected the blue connector, used a pin (see last photo) to allow me to check continuity. I knew I was looking for a break between the three wires that were under the screws on the back of the speedo. One end of the continuity tester wa on that, the other was on the pin, checking each terminal of the blue connector.

I first tried the middle (brown) wire on the speedo. Nothing. I then checked the left, found a hit. Then the right, found a hit. Back to brown, nothing.

I then proceeded to slice open the rubber sleve the wires were packaged in. I started from the bottom (should have started on the other end!). About 7 inches from the top end I found two black wires going into shrink wrap with nothing on the other end. Then I found the other end.

This picture is blurry - sorry!