I got a new tach I'm having trouble getting working. Can I just pop the hood, hook up the negative on the tach to the negative on the battery, the positive on the tach to the positive on the battery, and the signal wire to the negative on the coil? I'd like to test with the simplest configuration possible, so I can then rule out what is wrong. I'd like to just do it all right there under the hood. Is there any reason I shouldn't do this?