PDA

View Full Version : Tach done gone cRaZy


DH9441
05-31-2012, 02:13 PM
I just replaced the original tach in the '85 S/S. The PO said it never worked. The new one works but reads WAY high. Normally 6K at just on plane then burys the needle at any speeds above that. Is there a way to calibrate tachs?

wrobins1
05-31-2012, 02:36 PM
Make sure that it is set to the correct number of cylinders. Most automotive tachs have a switch on the back for 4, 6, or 8 cylinders.

Table Rocker
05-31-2012, 02:37 PM
Some tachs have 4-6-8 cylinder modes. You may be set up for a four. Your coil is firing twice as many times per revolution as a four cylinder's coil would. That would explain seeing double values. See if there is an adjustment on the back of your tach.

Got beat by trobins.

ski_king
05-31-2012, 02:39 PM
^ X3

I bet it is set up for a 4 cylinder.

DH9441
05-31-2012, 11:14 PM
Ok, I don't recall seeing an adjustment but I'll pull the cluster and check the tach again. TY-

DH9441
06-05-2012, 10:50 PM
That's it!!