Low-Fuel Indicator Fixes Itself

[Abner Mality]

I have been the proud owner of a 1980 300SD for nearly two years. In all that time, the low-fuel indicator lamp has never worked. I've searched the topic, here, and have intended to check the sending unit when the weather gets better. Yesterday morning, VOILA, the indicator lit up for the first time. My needle was a good 1/8" above the "R" on the guage.

About two months ago, I actually ran out of fuel with the needle in about the same position, so I am sensitive to the fuel level.

It seems I have two problems: the fuel guage doesn't accurately represent how much fuel is in the tank, and, now, the low-fuel light has "fixed" itself. Life is not this simple.

Any ideas why this is happening, and what would you veterans suggest I do to improve the credibility of my fuel guage?