Well I noticed yesterday when motor is off, tach still reads 1000 RPM.I'm still going to make sure the wiring is good to it . Probably will be searching for a tach.
Normal operation if tach. go's to 0 with key on.
Might try this. On back of Tach is small rheostat screw that is used to adjust tach. for different cylinder configurations. Sometimes rotating this rheostat screw several times and then returning it back to the 6 cylinder position will fix a malfunctioning tach.