Ever get back to this project? By the way, the circuit drops the extra resistor out at High voltage, not low voltage.
At Low voltage the 2 16 ohm resistor are in series giving a 32 ohm equivalent. As voltage goes above 13V the transitor turns on shorting one of the resistors out and giving a 16ohm equivalent resistance.
Which is interesting. At low voltage you get 2 low watt elements, and at high voltages you get one high watt element. G
