LIKE FRISCO SAID CHECK CONTINUITY ON THE BUTTON.IF NO READING YOU DON'T HAVE ANY POWER TO IT.IF YOU HAVE POWER TO IT SWITCH OUT THE BUTTON(AUTO ZONE ETC. SHOULD HAVE) IF YOU HAVE POWER AND THE SWITCH IS FUNCTIONING,TRY TURNING OFF THE IGNITION AFTER PRESSING THE BUTTON AND REPEAT TO GET THE HELLO TO SHOW.I WAS TO THE POINT OF RETURNING THE ELEC. SPEEDO AND GOING TO MANUAL TYPE.I KNOW YOUR FRUSTRATIONS AND IT AIN'T NO FUN,PARDON MY FRENCH.THE TECH PERSON SPOKE WITH SUCH AN ACCENT AT TPI THAT BEING FROM TN AND TX.I COULD NOT UNDER STAND HALF OF WHAT HE WAS TRYING TO TELL ME.I FINALLY JUST SAID HOLD TO ON TO YOUR PHONE WE ARE GOING FOR A RIDE.AFTER A WHILE WE FINALLY GOT IT TO CALIBRATE.LOL OH ANOTHER THOUGHT YOU HAVE TO REALLY ALIGN YOUR FOCUS TO THE LCD AS THE READING COMES UP.

Don In Austin