Where to start troubleshooting a bad tach
 

One year old and the tach stopped working. Where should I start looking?
Of course I checked behind the dash and its getting 12v power but I stopped there.
Any ideas what to look for next?

First question is which wiring harness do you have? Is it a 10 pin harness plug or the 14 pin? Does it have a digital to analog converter to work your gauges? Things aren't as simple as they used to be. Easiest thing is to connect a known good tach to the signal lead and see if it works.