The heater might start turning on and off frequently. This is called cycling. Cycling occurs when the temperature in the area around the heater is extremely close to the temperature that the heater is set to maintain; as such, slight temperature changes can cause the unit to cycle on and off. Slightly raising or lowering the thermostat can usually reduce this effect. Note: The heater will cycle more often in a High heat setting then in a Low heat setting because the air heats up more quickly.