Hmmm... that has me thinking. The LED's do use less current than conventional bulbs, which is desirable, but is a problem for standard turn-signal flashers, which need enough bulb current to flash. If these are "replacement" type bulbs, the LEDs themselves probably won't supply enough current for thermal flashers, so they might have a shunt resistor on the brake/turn "filament" in order to draw enough current for the thermal flasher to work. If this is the case, then you're back to square one...