Okay so I have been having trouble with a factory repro tach in the gauge carrier. It works, it doesn't, etc... So I hooked it directly to the battery and neg coil post out of the carrier - it works. I started piecing it together, testing it along the way with my wife and once I screwed it into the carrier - no workee.

To cut to the chase, after much troubleshooting, we narrowed it doen to when the metal backing of the tach connects with the gauge carrier, it stops being grounded. I shoved a piece of plastic in between the metal backing and the carrier and it works fine. Does anyone have ANY idea why this could happen?

Apparently, the tach chassis should not be grounded. Keep it isolated and should work for a long time.

Apparently, the tach chassis should not be grounded. Keep it isolated and should work for a long time.

weird. right in this case, but not right, as the tach chassis was designed to be grounded. Still, whatever works, right?