Stuart's on the right track here but Mr. Ohm says that if you half the voltage on any given load, the current will also be cut in half. My guess is that if the flasher works at all it will be very slow. I may be wrong about this also (never tried to do this) as the 6V bulbs will also be a different resistance than 12V bulbs and that may give the flasher enough current to work just fine. Give it a try and report back, we need a good electronics lesson today!