As a customer of Lefu Company,when you meet the heating problem, pls try the following step to check which spare part has damaged to lead heating problem to occur. Step 1 Check the heater fuse. PS: We provide you spare fuse at the spare parts box. Please find it to replace. Step 2  Check the Electric Relay PS: If this step1,2 is OK, please follow step 3. Step 3 Change temperature controller 1.Temperature controller                    2. Fix the temperature controller with screws 3. Plug the wire onto the main switch PS: We provide you spare controller in your spare parts box, you can find and replace it.