Check whether the light wave power supply is 220V, and if so, check whether the resistance of the light wave tube is normal. If not, if yours is a computer-based one, check the lightwave relay. If it is a mechanical one, check the timer and thermostat. If your lightwave furnace also has a microwave, check the magnetron and high-voltage fuse. (Before checking, first make sure that the transformer primary has 220V AC power)