It makes sense to track TACH hours as that does roughly track actual engine wear.
What I'm curious about is if all tractors monitor TACH hours or are there any true time hour meters out there?
The newer tractors have the potential for listing actual hours. If they have an on board display, they can list the engine hours according to the ecm.
Lofa industries and controls inc both have engine control panels that read true hours. If the motor has an ecm, then it reads actual engine hours according to the ecm. Even if a new panel is installed. If they aren't hooked to an ecm, then they use the altenator to determine that the motors running and start ticking hours. Both are pretty accurate. Of course if it's not hooked to an ecm, and the board goes out. Then the new panel is gonna start at zero. Lofa just added a feature so i can go in with a lap top and adjust the new panels hours along with calibrating them for deutz, deere, or catipillar sensors. I could probably do a few more, but thats all our liscensing allows
Murphy and a few other manufacturers have a 12 volt hour meter that just hooks to power and ground. Of course if the keys left on then it keeps ticking. Some manufacturers make a combo unit to except a tach cable and use 12 volt for the hour meter.
For most of us out there, our best options are gonna just give us a best guesstimate