The high current, under such circumstances, is not weird at all. . . .

EDIT
A LOW, B LOW => motor off
A HIGH, B LOW => motor turns in one direction
A LOW, B HIGH => motor turns in the opposite direction
A HIGH, B HIGH => black smoke.
The high current, under such circumstances, is not weird at all. . . .

EDIT
A LOW, B LOW => motor off
A HIGH, B LOW => motor turns in one direction
A LOW, B HIGH => motor turns in the opposite direction
A HIGH, B HIGH => black smoke.