The only thing that comes to mind at this moment is a high resistance short which causes an abnormally high current demand which causes the flasher relay to cycle faster, and simultaneously "starves" the bulb of adequate current to attain normal brightness.
A flash or beam of light
possibly bad earth on the indicator circuit, or poor output from the generator. check the voltage when running at the battery, should be around 13 volts. if ok, check all the earth points. Hope this helps.
shinny shine, flash, sparkle, glare, gleam, shimmer, twinkle, glint
you most likely have a short somewhere in your wiring
They were very dim, bare, and clear. They burned out fast.
the speed you are travelling in a vehicle is faster than your headlights are allowing you to see in front of you. If your headlights were very dim and you could only see a very short distance ahead it would be very easy to overdrive your lights. Or like running as fast as you can, in the pitch dark, in a place you've never been before, with a flash light that is so dim you can barely see 12 inches ahead
depending on the year of the vehicle, it could be a voltage drop running through the multi-function switch. Both the turn signal indicators and the high beam indicator are handled through the lever on the column. If your vehicle is an older vintage with the dimmer switch on the floor, check underneath the switch for rust and corrosion.
check for a loose ground wire
The rule of the road is to flash your high beams to remind them to turn their high beams off.
Just by reason of sheer bulk. He was not too fast , had dim vision , and wasn't very bright.
The light stay dim long as the cards is piled on top of the flash light. Human eye can adjust to see better in the dark and it might cause the thinking that after dimming by piling card over flash light for a while and it go brighter a little.
Remove the alternator and have it tested at any auto parts store?