Tach help needed

[custom10nut]

I just replaced my printed circuit to get all my lights working again.
My problem now is my tach reads about 500 rpm low at idle.
There's no way my engine will idle at 200 rpm.
Everything worked and the tach was real close to spot on, before I took my dash apart to change the bezel and do some other things.
Is there something I need to adjust other than the screw in the back (it will only adjust about 100 rpm).
Any input will be greatly appreciated

[Custom/20]

Originally Posted by custom10nut

I just replaced my printed circuit to get all my lights working again.
My problem now is my tach reads about 500 rpm low at idle.
There's no way my engine will idle at 200 rpm.
Everything worked and the tach was real close to spot on, before I took my dash apart to change the bezel and do some other things.
Is there something I need to adjust other than the screw in the back (it will only adjust about 100 rpm).
Any input will be greatly appreciated

Be sure to check all your grounds. Make sure your tach housing is also grounded.

[custom10nut]

Thanks, will do. I'm going out of town for a few days, but will do the grounds when I get back.
Do the two small screws on the tach face have anything to do with its operation?
This just really frustrates me, because it worked so well before.

[Custom/20]

Originally Posted by custom10nut

Thanks, will do. I'm going out of town for a few days, but will do the grounds when I get back.
Do the two small screws on the tach face have anything to do with its operation?
This just really frustrates me, because it worked so well before.

Those two screws on the front are only there to hold the faceplate on to the tach its self and do nothing about operation. The only thing that can change the reading is the adjustment screw on the back. If the tach wasn't adjusted then to only thing I can think of is a ground. If your power and tach feeds are secured and have good connections then its gotta be a poor ground. What I did was run a ground wire from the middle stud on the back of the tach housing to the lower steering column cover bracket that screws to the dash.

[custom10nut]

You rock! again thanks for the insight. I'll update when I get back into town next week