Okay for some time now my Tach will mysteriously start jumping ALL over the place no matter what my rpms are for no apparent reason....hell on ocassion it will even move up and down when i cut the blinker on!?!?! So bein the incredible engineer I am I just knock the crap outta the top of the dash and it begins working correctly. Well today I noticed the problem and I also noticed the water temp gauge will drop while the tach is goin all over the place and after I slap the dash it goes back up to its normal postion. Can someone please tell me what the deuce is goin on?!?!?!

 

well if it moves with the blinker sometimes you might have a short somewhere back there, take out the cluster and look, also check your grounds, crazy stuff happens when they break...

 

Most likely a loose plug or torn trace on the cluster.
90% chance your problem is in or around the cluster.
Just pull it, clean all the contacts with alcohol and q-tips and put it back together to see if that fixed it.

 

Thats what I figured...gonna pull that bad boy out tomorow and take a gander at it

 

Mine jumps from 0 to around 3000RPM(engine not running) if I turn the key off slowly. It works normal all the rest of the time, though.

 

Ground issue 100%