I have a 1966 that is having a problem with the high beams. The headlights are working fine, as are the high beams, but only for about 2 minutes. Then all the lights cut out. If I switch back to the low beams, the lights come back on. If I switch back to the high beams, they stay for about 5 seconds and then the lights cut out again. What's up? I remember seeing something about this before, but I don't remeber where.