I bought a glow shift shift light with tach reading in the middle I hook it up to my car and it won't go over 3000 I hooked it to the tan wire on the coil. I took it over to my buddy's car today and hooked it to the coil and it worked fine I came home hooked it to my car again and had the same problem. But I have all new gauges in my car from fl 5.0 I hooked it to my tach and had the same problem can I hook it to the ecu and get a different reading?

 

come on someone has to have an idea i'm at the point of throwing the shift light away