I am on my second Dualit kettle (matching toaster combo!) in a year, as both kettles started cutting out mid-boil - very frustrating. I have discovered they are v simple inside but have 3 thermostats (ie round metal disks that bend/click when they reach a set temperature), knocking the switch off. In the Dualit's case, there is one disk near the main on/off switch that steam flows down over (from the tube inside the jug-part of the kettle), which turns the kettle off when the water hits 100 deg C (ie full steam). The other 2 disks, which are the cause of my problem, sit flush against the underneath of the element and are the 'boil-dry' safety protection. I assume these are supposed to 'pop' at a temperature higher than 100 deg C but for some reason are activating below 100 deg C (perhaps poor quality or wrong components). When either of these thermostatic disks 'pop', they lift a pin which separates 2 metal contacts (like the points on an old car, if you are familiar), turning the kettle off. As with all such disks, when they cool, they return to their original shape, allowing the kettle to be switched on again. Anyway, all it takes to fix this particular problem (at zero cost) is removal of 3 screws on the plastic base, then careful squeezing of 2 black plastic ears inside the external plastic switch to allow the switch to be removed, then the bottom tray can be slid over the protruding inner switch 'prong' and lifted away. Three more screws allow you to lift away the internal switch assembly from the heating element. You will find 2 thin metal disks covered in heat-conducting white grease (these are the boil-dry thermostats which need to be removed). Use a sharply pointed knife to lift each disk's central prong off off its tiny locating peg and slide the disks out with a thin pair of pliers or strong fingernail. A tiny white plastic push-rod will drop out (x2) when the disks are removed. Bin the 2 disks and tiny white white push-rods. When reassembled, the kettle will now function correctly, turning off at 100 deg as you would hope, but please note the kettle now has NO BOIL-DRY PROTECTION so always ensure there is water in it and the lid is properly shut before turning it on (fill it through the spout if you think you might forget to close the lid). Best option is to get a new kettle under warranty; however, if you are desperate, and don't want to spend another £85, this is a simple solution (at your own risk clearly).
Life Hack
May 2017