I have an 89 mustang gt and the guy who had it before me put a tach in.I was wondering if the tach is supposed to bypass the original tach in the dash because that tach doesnt work in the dash only the one the guy put in does?

 

I believe it usually does bypass the stock tach, because the wiring for the stock tach is then used for the aftermarket one.Someone correct me if I'm wrong though.

 

yeah...the reason i thought of that was because i watched a video on you tube and noticed the guy had the same setup as me and both of his tachs worked so i didnt know if there was a way to get the dash tach to work also? Thanks for your input!!