Hi all. I have a ‘75 CL360 and the tachometer isn’t working. When I turn it on it shows about 1,000 rpm but no matter how the engine is revved (stationary in neutral or on the road), the gauge doesn’t move. I don’t really understand how the system works to connect engine to gauge, so I figured I’d ask before I blindly took it apart. How does it work? What are some steps I should take to figure out why I’m not getting rpm readings? Thank you!