Tack not working correctly on my T300

[8x56mn]

I have a T300 with about 200 hours. Bought it new 3 years ago. Just got it back from a new dealor where I had it serviced. When I went to start it up the Tack indicated 2000 at idle and goes to the max when reved up. When the tractor is shut off it goes doen to 1000. What could be causing this?

 

[MrChris]

Do you know if the tach is electrically or mechanically driven? I had a similar issue on a different brand of tractor. After running the tractor near pto speed the tach would climb to 3000 rpm but the engine speed did not change. Throttled the engine down to idle but tach would read 2000. Shut the tractor off and would be OK until I raised the rpm up. Would happen intermittantly but fortunately it eventually acted up for the tech. They had to replace the instrument panel. Thought it might be electrical in nature but it turned out my tach was mechanically driven and something inside the tach was acting up. Fortunately it was covered under warranty.