Your flasher is designed to operate with a certain amount of current flowing through it; this current also flows through the turn signal lamps.why we require flasher ? because at indicator bulb point i am getting flasher output, inside indicator housing if we put constant current circuit with LED would be enough.
The current heats up a bi-metal strip inside the flasher, which when heated enough, disconnects the current from the lamps. As the bi-metal strip cools, the current to the lamps is again connected. The cycle then repeats at a 1Hz-3Hz rate.
The current through even several LED strings is so much less than that of a pair of turn signal lamps, there would not be enough current to heat the bi-metal strip in the flasher, so your turn signal LEDs would not flash; they would stay on until you turned off the switch.
Try removing one of your turn signal bulbs, and you will notice that the other remaining bulb either does not flash at all, or flashes very slowly.
I obtained the values for the resistance, etc. for the last circuit by modeling it in a PSPICE simulation.As for as head lamp is concerned it serves as standby (i will retain standard head lamp),
it would be helpful if give me constant current circuit along with formula to calculate resistors value with respect to LED's ratings
The transistors which were used in the last circuit have a practical current limit of about 100mA. I do not know what you are planning on using for the "auxiliary headlamp" LED, but anything remotely approaching "useful" light output would require at least several amperes of current. You would need a much more sophisticated (and complex) circuit. It would not be a beginner's level project.