Technical Flickering headlights- really dumb question

Just a thought- if you have just put this back together, is there too much paint on your connections, thus not making an adequate connection ?

 

unless i missed it, i have heard heat mentioned yet. usually a bad connection in a component like a dimmer switch will be hot to the touch from the resistance. same with the ground wire.

 

Since you lost high beam altogether, sounds like the dimmer switch has died. All it does is switch the current between the high and low side, it’s probably corroded and melted inside. I had one with similar symptoms as yours one time, first the lights flickered a few times, then I lost both high and low. Mine was the feed wire deteriorated over the years and finally burned in two.