It's not idiomatic to say that the car is broken. We speak of "a broken window, headlight, axle, door handle, fan belt, radiator hose, etc." When something fails to operate properly, we say it doesn't work. If we suspect it may be easily repaired (as opposed to "replaced") we'd more likely say "it's not working ." (the radio, alternator, air conditioning, defroster.) If it needs to be replac