No tach, tried new sensor.

Each time you turn the key to the run position, your tach should self check or show needle movement. I would start by verifying power (12v) and ground at the tach head before you condemn the head.

 

First verify ground at another terminal as the tach head also grounds through the plug.
If you have both power and ground, then the tach should self check when the key is cycled on.

To verify ground connect test light clamp end to known good 12v and probe for ground (use your test light backwards)

 

FWIW, with my last company, I got assigned an old truck that the tach did not work on. I wrote it up three days in a row, and the shop never even looked at it. So I stopped writing it up, figuring it was a waste of time.

I went out on back surgery and another guy was driving that truck. Got pulled in for an inspection and got an OOS for the tach not working. Then it got fixed.

Of course he got in hot water with the company. We had a standing policy of days off for an OOS. When I came back to work and found out about it, I went into the files for the write ups for that tractor. They had been removed.

I know this has nothing to do with you getting your tach working, it is just something that has always eaten away at me, and this looked like a good chance to bellyache about it.

 

Yep, you narrowed it down to the guage.