How to Test a Dishwasher Thermostat

Open dishwasher full of dishes

A dishwasher thermostat controls the temperature of both the water and the drying cycle. If you've noticed that your dishwasher is leaving you with wet dishes, or it doesn't seem to clean as well as it used to, the thermostat may be malfunctioning and can be easily checked.

Step 1 - Run a Diagnostic Test

Many newer dishwasher models will have a way to run a diagnostic test. This will eliminate the guesswork and let you know if the thermostat is operating properly. Some dishwashers have a button you can press for a diagnostic, while others will have a specific series you must follow to start the diagnostic test. Refer to your owner’s manual for information on how to do this.

Step 2 - Hot Water Thermostat

If the dishwasher is giving you poor cleaning results, the water may not be heating properly. You can check the temperature of the water heater to ensure it is high enough. You can simply run the hot water in a sink for a few seconds to test the water temperature. If you do need to adjust the water thermostat be sure to keep it under 120 degrees. Exceeding this temperature can cause burns/injury.

Step 3 - Run the Dishwasher

If your dishwasher allows you to set different temperature settings, try to run a short cycle on the highest heat temperature. If the dishwasher doesn't run through the dry cycle properly, the thermostat will likely need to be replaced.