Greddy Turbo Timer; falty speedometer reading.

[Dan Powers]

Hey, does anyone know what could cause this thing to malfunction by displaying an incorrect spedometer reading.  The timer is connected to the car just with wiring a harness.  Maybe a loose connection somewehre?  It worked fine before, I moved it with out cutting any wires & it stopped working for a bit, now it is working again.  Soo odd..

-Thanks!