Spent the night swapping the diesel gauges over to my 62 dash. The important one I needed was the tachometer due to how the diesel reads RPM. On the 62, the tachometer gets the RPM signal from the ignition coil.  Since the diesel engine doesn’t have an ignition coil, you have to get the RPM’s from either the alternator, fuel injector lines, or by the factory setup, the flywheel. It uses a Hall effect sensor which is a type of transducer that varies its output voltage to the tachometer in response to a magnetic field. Basically it detects the teeth on the flywheel as they pass the sensor and converts that signal to the dial you see on your dash.  Read more...