Do you have a GPS or can you borrow one if you don't?

And if you have V4 of the speedohealer (or whatever earlier ones didn't have microswitches) it will tell you which buttons to press in the proper order step by step to program it.Mount GPS so you can see speed on it. Go to 70mph indicated on GPS and keep it as steady as possible for at least 10 seconds. note your speedo number.
Go to speedohealer website and put those 2 numbers in web form, it will tell you microswitches position, no guessing no errors. I did mine and it dead on now.
