It occurred to me that my short post looked flippant or snobbish, but let me correct that. I do all of the repairs on my electronics, computers, tv's, everything I've bought since about 1980, and I do tend to try inexpensive stuff so I would fix it if I could. But I've tried a couple of cheap wireless speedometers, with no success. . What I mean by "toss it" is that based on those, the probability that it will work right for more than a month or two, times the $15 to replace it, should be valued less than the time spent messing with. Change the batteries if you have them, move the head unit to a different location, if that doesn't work I recommend an inexpensive wired Bell or Schwinn which are every bit as good for basic functions as more expensive ones.