I had the same issue with my 81 years back first thing is check the sockets with a tester to make sure you have current going to them,the bulbs are 194`s if you are going by old bulbs which might be blown buy new ones,if you got current and good bulbs and they still don`t light the next thing is your oil pressure switchs which are wired to the light bar,they might need replacing which was my issue way back when,there are 2 a high and a low oil pressure switch if you follow the wire from the light bar you`ll find them I got them from Rock Auto but that was 5yrs ago I know the 301 store carries them