4kq- wires to the speedometer?

[a4kcstq at comcast.net]

I've been trying to locate a strange clicking noise in the instrument cluster of my '86 4kq.  I've eliminated everything except the gauge cluster itself.  I've notice a couple of wires on a 2-pin plug at the back of the speedo.  One wire is white w/ blue stripe, and the other is brown (ground?).  I haven't followed them to see where they go into the dash.  The weird thing is that Bentley has no such wires in the schematic.  Does anybody know what these wires do?  Inside the speedo is small coil (electromagnet?) next to the rotating hub.  What the heck is that all about?  I thought the speedo was driven only by the speedo cable.
-Peter