Oil light on.changed oil,filter,and oil sender.

The big question is, do you have oil pressure on your engine? If your engine has no oil pressure, the lifters (tappets) will clatter loudly. There won't be any doubt that there is something wrong. As long as your engine sounds normal, something is probably telling a lie.

Now, to test the sending unit, connect a DVOM (digital volt ohm meter) to the sending unit and the a good engine ground. Put the meter's function switch in OHMS , R X 1. You should show infinite resistance. Now, start the engine, you should show zero or very low resistance. If you don't know what "infinite" resistance looks like on your meter, with the meter set in the correct function position, touch the meter leads together. This is contineutity or zero ohms. Now, take the meter leads apart. This is infinite ohms or an open circuit reading.

If you sender is working, you need to trace the wire and look for a short circuit grounding the wire somewhere. If you are still unsure, take the sender unit back out. Start the engine and allow it to idle for a few seconds and pump a few ounces of oil out. Shut the engine off and reinstall the sender. This is how you break a "air lock" in the oil pump. These are common on Softail and Sportsters but not some much on you RK.

Good Luck
Steve