With a multimeter measure to see if there is power coming in to the heater. Then disconnect the power and measure the resistance of the heating element itself probally something like 10 to 15 ohms. If you don't get a reading a second check would be continuity. Set the meter to continuity and measure accross the element. No continuity means the element is open and needs to be replaced. If you have continuity then you need find why you are not getting power to the element ie Fuse, breaker, broken wire, lose terminal, corrosion or thermostat. With your meter just follow the voltage through each device and see where it stops. If you are not comfortable with using a multimeter then take it in and have someone fix it. Don't get shocked!!!!!!!