I HAVE A AUTOMETER COBALT TACH THAT IS CONNECTED TO THE COMPUTER. IT IS ON A 98 COBRA. IT DID WORK FINE TILL THE OTHER DAY. THE TACH STILL LIGHTS UP BUT IT DOES NOT GO UP AND DOWN WITH THE RPMS. THE NEEDLE JUST SITS AT ABOUT 2K ALL THE TIME. WHEN I PUSH THE BUTTON TO CHECK THE SHIFT LIGHT IT STILL LIGHTS UP, ALSO THE LIGHT WILL ENGAGE WHEN THE CAR HITS THE SET RPMS. ANY IDEAS ON WHAT THE PROBLEM COULD BE.