You might have to take the kick plate off of the bottom to do this. Once isolated from the mains, identify the heater element from the under side. Disconnect the wires going to it and with your multimeter check that the heater has gone open circuit. You will have to do the same for the NTC device. This is the thermal cut out wired in series with the heater. One or both these items may have failed. You might have to take the kick plate off of the bottom to do this. Once isolated from the mains, identify the heater element from the under side. Disconnect the wires going to it and with your multimeter check that the heater has gone open circuit. You will have to do the same for the NTC device. This is the thermal cut out wired in series with the heater. One or both these items may have failed.

If this sounds to much for you, it is probably time to get an engineer in ;) If this sounds to much for you, it is probably time to get an engineer in ;)