Tachometer reading incorrect RPM

[SpooledUp]

My tach had been reading incorrectly for some time now so I finally got a recalibrated unit from Caspers and replaced it. To my suprise it did not correct my problem. The question I have is there a way to adjust this unit that I missed when I installed it? Is there any other things that I should look for that could be causing my problem? Any info is appreciated.

 

[garyk1970]

Make sure the tach and fuel pump test leads behind alternator are not pluged into each other or anything else.....long stretch...but common.