I have a 1988 560 SL, 137K miles. Black/Palamino Leather

To get started, The tachometer is not working (at all) and I am seeking advice on how to repair it.

First steps/first item to check and how to do it. Is there a sensor or pickup that I need to check...trace, locate? All/any advice will be greatly appreciated.

Other than that, I Just bought the car, always dreamed of having one..love it already and now its time to start getting smart (aware of and addressing issues, learning from forum members, others, etc ) and and getting on with repairing & restoring it.