high heater speed doesn't work. (Page 1/1) richard in nc AUG 28, 04:16 PM i tryed searching.only the high speed on my heater doesn't work.i pulled the board out with the three coils on it.it 'looks' fine.owm meter says none are burned out. 1985 Fiero GT AUG 28, 06:14 PM quote Originally posted by richard in nc: i tryed searching.only the high speed on my heater doesn't work.i pulled the board out with the three coils on it.it 'looks' fine.owm meter says none are burned out. The coils are for the lower speeds, high speed is just 12v straight to the fan, could be a wire, or the switch maybe.