Dishwasher thermostats cost relatively little, yet they can make the difference between a dishwasher working effectively or malfunctioning. There are various ways of diagnosing a faulty thermostat, including observations, using test strips and employing an electronic measuring instrument. Take care to act safely at all times, disconnecting the dishwasher from the mains before commencing any disassembly work.
Function of thermostat
A dishwasher thermostat regulates the temperature of the water during the wash cycle. In the case of most dishwasher models, cold water enters the dishwasher and is then heated to the required temperature. The thermostat is basically a switch that opens and closes as certain temperatures are reached, keeping the water at a constant temperature. Thermostats are also employed in the drying cycle of the programme, to regulate the temperature of the hot air.
Indications of thermostat malfunction
Stop the dishwasher after the pre-wash cycle or about ten minutes into the main programme. Open the door. If the water seems too cold -- indicated by the absence of steam or a lack of heat being emitted -- it may indicate thermostat malfunction. Similarly, this could be the case if the dishwasher does not complete its programme or fails to dry the items adequately. You can use dishwasher thermometer test strips to measure temperature more accurately. Stick a label on a plate, then place it in the dishwasher. At the end of the programme, if the white panel has stayed white, the water did not reach the required temperature.
Removing the thermostat
Different dishwasher manufacturers use many different thermostats. Familiarise yourself with the appearance of your dishwasher’s thermostat before beginning this job so that you know just what you are looking for (see the link in the Resources section). Switch off and disconnect the dishwasher. Remove the cosmetic skirting board, if present. Remove the access panel screws and the panel. Remove the toeplate or kickplate if necessary. Locate the thermostat. Unscrew it, disconnect the terminals or unplug it as necessary.
You can test a thermostat with a multimeter, according to eSpares. Check the instructions to calibrate the instrument correctly before starting the test. Set the dial to zero. Place the red and black probes on the thermostat’s terminals. The reading should be close to zero. A high reading or no reading indicates a faulty thermostat.