Diesel Tach, What makes 'em tick?
 

I am restoring an 86 with a 6.9. My tach is all over the place and below zero at idle. How can I trouble shoot thiss issue? Also does anyone know of an aftermarket tach and sender that will work. I am considering doing away with the entire stock instrument cluster and fabricating a costom panel from scratch. Any insight or a good vendor for the guages and senders would be great.

yers prolly reads from the cam sensor????

go to this joint

Tiny-Tach: Diesel Tachometers

they sell one that has a transducer that bolts to any injector line to read the pulses.........................easy man :5:

If the 6.9 is the same as the 7.3 idi, then it picks it up from the injector pump timing gear right on top.