I am having a problem with my 67. The tail lights and directional's work properly with the headlights off. When I turn the parking or headlights on, the two lights on the right side are bright (like the brake pedal is depressed) so you aren't able to see the directional or brake light. The two lights on the left are working properly all the time. Any idea what my problem could be ? I just changed all 4 sockets and still have the same problem.

 

On the not-correct working side, swap the two power leads.

 

Thanks !!