Fridge freezer refrigerator Defrost heaters

Defrost heaters are fitted to units with automatic defrost systems they use a timer mechanical for older fridge freezer units and digitally controlled for more modern machines.

The heating element is just the same as any oven element.

A resistive element is encased in a insulated material and then surrounded by an outer metal protective casing.

Elements can fail and usually fail open circuit or Ol on the meter if intact you can work out the ohms reading by the wattage of the element and the volt with ohms law. With these elements is always good practice to insulation resistance test them to check for earth leakage currents.

These element need a timer to turn off and some sort of control be it a thermostat or a digital sensor. There is usually some sort of thermal cut out protection and a thermal cut out fuse is used to disconnect power if the device should overheat.

Thermal cut out fuses can be tested for continuity and replaced if blown remember to check for any reason the fuse blown maybe insulation resistance of element has failed or water ingress always best to check. When replacing the fuse make sure you fit it exactly where it was before to prevent nuisance tripping.

Old units will use a mechanical timer to turn the defrost element on-off today electronic programming is used.

Visually check to see timer operation to confirm its working or not if its not or its getting noisy in operation them replacement is only option.