Nomenclature: in addition to our language difference.
The lights do not change from dim to bright and back. They go from low to high!! Distance focal point change!!! Best seen in the dark. I use my light colored garage door! From about 20 feet or so, aim at alight surfacel Lights on. Change from high to low and back. You will see the pattern. I adjust the focua in that manner.
As to poor connections.
- Under the fuse box in the engine bay on the left wing wall slip the fuse holder from its retainer. Scrub the underside with contact cleaner or similar. some advocate resolder of the joints.
2 At each lamp. The holder that plugs on to the amp lugs. it may be corroded. I was displeased with mine.
I got new ones from Rock auto and soldered them in.
Swap in new fuses. Note the numerical value chart to get proper ones in USA speak.
Twenty years ago, I would swap in a fuse box for modern fuses and dump the glass tubes!!