What Is the Purpose of a Thermo Fuse in a Dishwasher?

Purpose

• In some dishwashers, the thermo fuse protects only the heating element by cutting power to that component if it overheats. In alternate designs, the thermo fuse protects the entire appliance -- wiring, motors and solenoids, as well as the heater -- because overheat can melt insulation, which causes very dangerous operating conditions. Technical data sheets often comprise part of the delivery package and service instructions and are available by model number on most manufacturer websites; check the data sheet specific to your dishwasher. If the thermo fuse is between the cord that comes directly from the outlet and the dishwasher door, your design is of the latter type.

How Thermo Fuses Work

• Thermo fuses work just like regular fuses, except they sense temperature rather than voltage drain. If they get too hot, they interpret this as an indication that the appliance is not functioning as it was designed to, and they protect the circuits by opening. They are also like regular fuses in that once they have opened -- or are blown -- they cannot be used again. They must be replaced.

Replacing the Thermo Fuse

• Thermo fuses are located adjacent to the control board on most dishwashers. They look like regular fuses except they are molded into a plastic housing. Thermo fuses are almost invariably sold with two wires attached to the housing; be sure to use the new ones to fit the replacement fuse rather than reuse the preexisting ones. Pull on the connectors, not on the wires themselves, to remove the fuses.

Fuse Attachments

• The fuse’s own attachments can cause it to blow. The two wire tails that connect to the housing are often the smallest gauge in the circuit. They can overheat and cause a false-positive that blows the fuse.