No problem.
It's a handy feature. Speedo needs to be powered up for it to work.
Go to the setting. Then rotate the pinion one 'click' at a time, the light on the speedo will change as you go from sensor to sensor (three sensors in total.)
At a guess you'll only get two of the three lights.
If it is the sensor this is what you need:
http://www.shopatron.com/products/pr...5942/745.0.4.3
NES5942
MiCk B. :-)