joobee,
There is several lights,but if your's is the one with the knob on top and the removable light shade then inside there will be two metal contacts. They are greased from the factory, and after years of use sometimes get gummed up and can even bend till they don't make proper contact.
You have to disassemble the light fixture and carefully clean it, then gently bend the little contacts back where they make proper contact.
There is no "kit" that I know of to fix them.
Joe