NY wrote:

I think most of the cars that I've owned in the last 20 years have kept the
dipped filament on when the beam is on.

You mean that twin filament bulbs are using both simultaneously?

What was the main reason that cars changed from sealed beam to replaceable
bulb in fixed reflector?

I think the cost of replacement was too high. Also it was a
design constraint, you were stuck with a standard shape.

Chris
--
Chris J Dixon Nottingham UK
@ChrisJDixon1

Plant amazing Acers.