I have a 1966 GTO with the standard 4 beam headlight system. When the high and low beams are on all 4 lights work fine. When just the low beams are on the passenger side does not work. What causes this and what is the cure?
This can be a bad headlight or a bad ground going to the headlight. Check to see if you are getting power with a test light to the headlight. There will only be on part that will makethe light work. Then if you are it's probably a headlight. If the headlight is very dim when the low beams are on then you need to clean the ground. Just follow the black wire back and it will be on the header panel, remove the bolt clean teh panel and the connection then reinstal it.