Testing the Thermistor on a Dishwasher

Safety

• Servicing an appliance while it's connected to a power source can result in serious injury or death. Although it isn't necessary to disconnect the power supply when running a diagnostics check, you should always unplug the dishwasher from the wall outlet or shut off the electricity at the breaker box before trying to access any internal components. Also, if the demands of the repair are more than you bargained for, don't hesitate to call an expert.

Diagnostics Check

• Some dishwasher models have a diagnostics mode that goes through and checks the various parts and settings to ensure they're functioning properly. The mode is usually accessed by pressing the control console buttons in a particular sequence. For example, you would press the "High Temp Scrub," "Air Dry," "High Temp Scrub" and "Air Dry" buttons to access the diagnostics mode in Whirlpool Point Voyager dishwashers. Consult your owners manual to determine the appropriate diagnostics button sequence for your dishwasher, as well as the button or icon that's used to indicate an open thermistor.

Control Board Testing

• If your dishwasher doesn't have a diagnostics mode, you can test the thermistor from the control board. This type of thermistor testing requires the removal of the electronic control console, which can be accomplished by disengaging the retaining screws or tabs. Remove the control board shield to access the dishwasher wiring. Detach the black-and-yellow and white thermistor wires from the control board terminals. A digital multimeter is used to measure the resistance of the component; touch the probes to the empty terminals. Readings between 48,000 and 52,000 ohms typically indicate a functional thermistor. Consult the tech sheet that came with the dishwasher to determine the ideal thermistor resistance for your model.

Thermistor Replacement

• Replacing the dishwasher thermistor requires the removal of the outer door and kick plate; these components might be secured with screws or tabs, depending on your model. The thermistor is attached to the bottom of the sump. Detach the two thermistor wires and remove the retaining screw to free the component. Installing a new thermistor is simple. Hold the replacement thermistor to the sump and replace the retaining screw. Attach the removed wires to the thermistor terminals.