I have a 69 Z28. I converted my aftermarket tach that was attached to the steering column to an in dash stock tach replacing the old fuel gauge in the dash. Now the tach doesn't work properly. I have tried two tach gauges and neither work. I believe the gauges are okay as they were purchased new.I have a 454 big block with MSD ignition could that affect it but the column tach worked fine and I used the the same electrical hookup. Thanks for any suggestions. Ray

 

moved your post to the first gen tech section. welcome to the forum. please read the rules and enjoy. thank you.

 

According to MSD, a factory type (non-aftermarket) tach may need a tach adapter to work correctly.
Read page 2: MSD Instructions

 

Did you modify the under dash wiring harness for the factory tach setup? The 69's also have a different printed circuit configuration on the back of the cluster for tach equiped cars vs non-tach cars.