fuel gauge or sending unit?
 

Good Afternoon
I do not know if this is the correct forum but saw none that listed the SE models.
I would appreciate some help with my 1971 280SE convertible.
How do I determine which model, W111, W108, W113? I have the vin. Does that tell me?
I have a fuel gauge that does not work. I have power to the sending unit in the trunk. I removed the fuel sending unit but it is a solid tube and did not know how to take that apart or if I should mess with it. The car sat in the barn for 10+ years so lots of things gummed up! I do hear movement inside the tube in the sending unit. I have changed all fluids. Car is running fine.
I was going to remove the dash cluster to check the fuel gauge wiring but got stuck. How do I remove the cluster? I read on the forums there are knobs on the back of the cluster that if removed would allow me to remove cluster but I cannot find any knobs. Not only that I have big hands for a woman but have no idea of how a mans hands would fit behind the dash. It would be alot more fun to drive if I knew how much gas I had!
Any help appreciated. I can order a new sending unit but hate to start throwing parts until I diagnose the problem
Thanks
Pam

Thanks
 

Thank you thought it was induction wire but did not know the ohm I wanted to read. Also still trying to figure out how to get the dash removed to check the gauge
Thanks for the help
Pam