my Low dollar 318 hop-up project

So with all the rain they are predicting for the next several days, I got a couple of hours on this nice day and I throw them at the Duster. I installed one of those Bosch tachs I bought about 4 months ago that the auto parts stores sell, and guess what? It doesn't work. Yes, I know how to hook up a tach.... LOL. I don't know where I bought it, no receipt, so I lost. I used to always run the "auto gage by auto meter" tachs and never a problem. 1st time with a Bosch, bad experience I guess. The light works, and that's all..... :( I wanted to see what RPM's I'm shifting at, and all. I've got some tweaking to do, but I want to start with a tach to be consistant...... I guess another day...