I've a  question: When two CFL's are switched in series, does the twice lamp work when one lamp is defect? Normally not, or?

i have seen PL CFL in fixtures strobing like a defect preheat fixture......they were wired like this.....digram I drew..... so what happens if one PL is defect is one would flash faster than the other....i ma not sure which flashes faster........but you get it........

If electronic ballasted then both will blow when 1 fails. The 2 in series with magnetic ballast both will flicker, change as a pair always. They can be hard to atart on low mains or when cold. For separate starters you have to use Osram ST151 as opposed to ST111 for 220V use.