tach on my 91 Mark VII is sporadic, malfunctioning
the tach on my 91 markVII is acting up it reads right for about 5 seconds the jumps to around 4 grand for another 5 seconds then goes back to the right reading and continues this cycle the whole time its running, just wondering if there is a ballast or relay for the tach that may have went bad or is it just the cmplete tach unit itself any input would b appreciated thanx
Ah! I know just the problem you're talking about. My Mark did that also. It is caused by a bad ground on one of the wires to your tach. The wire is orange and can be located right behind the kick-panel near your fuse box. There are two bundles of wire -- it is the orange wire in the smaller bundle. Also, your fuel gauge will no longer read full all the time.