[Healeys] Tachometer? or tachometer cable?

[raymead at comcast.net]

hi all



sometimes my tach, at idle, reads around 800rpm and other times it reads
around 2,000rpm (so, once you accelerate, at times it reads the correct rpms,
and at other times it seems to read about 2,000rpms too high)..............



is it more likely to be the tach itself, or the cable???B B B 

any quick tests that your basic MECHANICAL IDIOT can do to eliminate one or
the other?



tks, ray (the mechanical idiot himself)!!!!!!!!!!!!!!