i looked at wiring diagrams and got a head ache so i am going to ask and maybe someone has the answer. the tach works but is way off...at idle it reads 4000 RPM even though its not running at that. it goes up and down as you rev it like it should just not correctly (if that makes sense) when the car is off it goes right to zero. when the ignition is on engine off it reads zero, at soon as it starts it reads 4000. what would cause this? coil? pickup? i am at a loss and it annoys me

 

anyone?

 

Look here:

https://www.thirdgen.org/forums/elec...meter-fix.html

 

86T/A_Ram_Air,

I would have to say it's the pick up coil that's giving an inaccurate reading.

 

thats what i thought but if you look through the thread posted above it appears to be the tach board, i guess i could replace some stuff before i tear apart the cluster, i would hate to modify a tach board for no reason if something else is actually the problem

 

Test the tach board resistor chip. It is an easy fix, & seems
to be a pretty common failure. I fixed mine last weekend by
the info in the sticky.