Bench testing a tach
 

The tach on my Grady wasn't working. I'm in the middle of doing some repairs so I can't check the signal from the engine. I tried to put voltage from a jumper pack to it but it didn't do anything. I tried the same thing with a known good tach that had a broken face and had the same result. Anyone know the proper way to bench test a tach?

You'll need a way to generate a pulsed signal.... Most practical way would be to hook it to an engine with a known good tach and compare readings