Woodheat, the tach works off your alternator. Normally it's a pink wire and provides a pulse stream based on rpm that is decoded by your instrument panel. If your tach is not working, it might be a failing instrument panel. There is no fuse that deals ONLY with the tach. If it was a fuse blown, you would probably not have any working gage or light on the panel. My tach on my TC45D sometimes sticks and I have to rap on the plastic cover of my panel to get it to come to life. Once it is working, it keeps working just fine.