Old car speedometers would do that too Ed. What happens is the cable inside meets resistance, winds up, then breaks loose and runs faster to catch up. During the many unwinding actions, the tach sees the increase speed and reads high, gets another spurt before it can slow down. I would suggest a look and lube first of all to see what happens, eventually the action will bust the cable. A brand new tach would only read the very same if the cable is the culprit..
-- In [email protected], "Ed Burkhead" <e...@...> wrote: > > > I'm having a hard time imagining that a cable problem could cause the tach > to read extremely HIGH. Low or no reading at all I could understand. > > (I had a few seconds pucker factor when my tach dropped to zero when the > cable failed very low over the trees during takeoff from Antique Airfield in > Iowa. Then I saw that the engine was happy and I returned to home base for > repair.) > > For it to read high, I'd bet that the problem is inside the tach itself. > > If your mechanic has a spare tach cable, it might be worth spending some > time installing the replacement cable to see if that solves the problems. > Those cables do fail and I know I had to replace one when my Coupe was new > (to me). But I wouldn't spend a hundred dollars of shop time testing this, > personally. > > Ed >
