tach on my 91 Mark VII is sporadic, malfunctioning


Asked by May 14, 2012 at 07:00 AM about the 1991 Lincoln Mark VII LSC

Question type: Maintenance & Repair

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

1 Answer


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.

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