Strange tacho problem
 

Hi all, just awondering if anyone else has had this issue before.....

When I first start my '82 the tacho has a mind of it's own. Sometimes it just sits at 0 RPM. Other times it indicates RPM a lot higher than the car is actually revving at.

Once the car is warm it works fine. All other electrics on th ecar work fine at all times. Car has new coils and new ignition modules and runs and drives fine.

It is almost like that there is an earth issue at startup, but gradually goes away???

Any ideas?