Just looking for a step by step guide to find out why tach doesn't work. I do have a generator and cable is hooked up to gen. I unhooked cable from gen and turned it by hand. Noticed some tach needle movement but it seems to move erratically and stick at different numbers. Movement of needle does not seem normal in relation to turning the shaft. Was thinking of spinning cable end with a cordless drill to check for needle movement. Any risk of damage with this method i.e. if I turn it the wrong way? Any better ways to test?