For what its worth, the illumination of the stall wrn off light indicates the possibility of heater failure of the AoA sensor, system signal failure and or electrical pwr failure..to determine which component of the stall wrning system is inoperative simply perform the TEST. If the light remains illum, then the heating component has failed..if the light extinguishes and the indicator fails to rotate, the the continuity system is inoperative....
The internal heating feature is only available when No1 Engine is operating and or air ground safety sensor is in air mode...
Hope this is of some assistance...