[ngrimm]

Thank you for the reply. I connected my oscillocope to the junction of d1 and r6 and at speeds below say 15 mph it is more of a rectified sine wave with a peak to peak voltage of about 2 volts. Once it hits 15 mph it is more of a square wave with a voltage of 3.5 volts which climbs to about 4.5 v as I increase speed. I tried a pot in parallel with the zener but still couldn't get the level high enough at low speeds. I also put a pot across the resistor but even at a pretty low resistance it didn't change much and I was afraid of it drawing too much current. I think I could make it work with an op amp set up as a schmidt trigger to make it a square wave. I guess that's the advantage of adding you own hall sensor since it is more of a digital output.