It is important to make sure you are running this device fully submerged in the water, and that you are able to see the heat coils turning red inside the glass tube. Please inspect the glass tube for any hairline cracks or damage and ensure the top is sealed completely and the cable connection looks okay.
The light should appear with a clicking noise when the heater is heating and then again once the tank has reached its desired temperature - the light may then switch off. When the temperature drops again, the same thing will occur
It is important to ensure the heater is big enough for the amount of litres in your aquarium. Heating all the water as desired. The general rule with our heaters is - 1W of the heaters power, will heat 1 litre of water in your aquarium.
If you come across any damage, please send an image to our customer services team who will be able to assist you further.