Tach problems

[duckzilla]

Hey. I'm slowly trying to recondition my ranger and the thing on my list now is a messed up tach. I have no idea where to start. I'm assuming it is wired to the coil somehow correct? Anyways. The tach sits around 3000 and when i floor it as i remember correctly. The tach jumps. Anybody have any ideas?

 

[92super4x4]

my tach is doing the same thing, except when the key is turned and the ignition is on, with the engine off, the tach will shoot up to 3k and stays there even after the truck is started. It has to be something with the wiring, anyone else have this problem?