I can only give my info learned that happened on my 72 cuda years ago. I went through the same issue. Everytime I hit the brights, they quit working. A guy at the dodge dealership told me my voltage reg was putting out too much and running wide open full charge. Turned out the ground was bad on the volt reg and was the culprit. I went through 2 regs before I finally got the gremlin. I changed all that everyone else said also