As I understand in the C152 was never fitted with a dual filliment light, the aircraft had ether one landing light in the nose cowl or two lamps in the leading edge of the left wing.
If you have a split light switch fitted and only the nose lamp fitted I would suspect that the wrong switch has been fitted some time in the last thirty years.
I will have a look in the Cessna parts book and see what I can find as all above is from memory.