Tachometer not reading much above 600

[AGH]

1971 3500 auto tachometer has started reading low and doesn’t go much above 600 rpm. Was reading ok before.Any advice.?

 

[mrtask]

Press harder on the gas pedal!
Sorry. I'll get my coat...

 

[quattro]

Sounds to me like an internal issue, do you have any auto electricians around your way?