A heater that inhibits the formation of ice in an air gap separating a stationary stator and a rotatable rotor of a rotating machine. The heater includes a plurality of stringers configured to be arranged in associated winding slots of the associated stator adjacent the air gap, and extending between two ends of the heater. Each of the stringers includes two electrical resistance heating traces arranged between two electrical insulation layers that are arranged between two thermal conduction layers. The traces extend along an entire length of each of the stringers between the two ends of the heater. The traces are electrically isolated from each other.