The Tach Cluster
by Erich Bozzer
How many times have you seen a Tach Instrument Cluster at a swap
meet and thought that it would be nice to replace your base instrument cluster? You look
further and find out that in order to perform this change you also need the unique wire
harness that goes with it. Then you learn that the wire harness is either missing or too
expensive. Anyway do you really want to tear your whole dash out to replace the wiring?
Good news, now you can modify your existing base wiring to be used with the Tach Cluster.
As you know, when the Tach was put into the right center pod of the
cluster it forced the temperature and fuel gauges to move to the two outer pods. Ford
replaced the charge and oil pressure gauges with warning lights. All these changes can be
summed up into 4 categories: 1) Pin-out changes in the connector on the back of the
cluster. 2) Oil pressure indication, 3) Charge indication and 4) The tach connection.
Let's start with the charge indication. The amp gauge is basically a
worthless instrument. How many times has it actually told you that your charging system
was bad? The warning light is not much better because by design it can only tell you when
the voltage regulator is not working. It does not indicate complete charging system
performance. Also, to switch over to the warning light is a major rework of the dash wire
harness as well as replacement of the short alternator harness. This information leads me
to suggest that the charge indicator in the cluster can be deleted. An add on voltage
gauge put in a hidden place is not only the easiest thing to do, it is also the best
charge system indicator. So, what we will do is: not use the amp gauge wires at the back
of the cluster, add an aftermarket voltage gauge (if desired) and leave the rest of the
charge system untouched. If you're interested in all the details to wire in the warning
light, write to us at the Registry if there is enough response, a future article may be
Now to the fun part. Just follow the step by step procedure in
proper order to install your new in-dash tachometer. Please read it through first so you
get the big picture before you start.