A malfunction in which the dishwasher does not heat water most often indicates a failure of the heating element or a failure in the voltage supply control circuit to the heating element. When you start the washing program, the device takes in liquid, but the wash cycle takes place in cold water, which leads to poor removal of grease and lack of disinfection of dishes. In modern models Bosch, Electrolux or Indesit the electronics may immediately block the program from starting or issue an error code if the temperature sensor detects no heating within the allotted time.
The lack of hot water in the tank directly affects the chemical reaction of the detergent, since most powders and gels are activated at temperatures above 40 degrees. If you notice that after the end of the cycle the glass remains dull and that congealed grease is visible on the plastic containers, this is a sure sign that heating water did not occur at all or was insufficient. Ignoring this problem can lead to clogging of filters and pipes with greasy deposits, which do not dissolve in cold water and are not washed off.
The main reasons for the lack of heating in the dishwasher
The most common reason why a dishwasher stops heating water is burnout. heating element (tubular electric heater). This element operates in an aggressive environment, constantly coming into contact with water, hardness salts and chemical components of detergents, which over time leads to the destruction of the nichrome spiral inside the tube. It is impossible to visually determine the breakdown; a “ring” with a multimeter is required, since even a seemingly intact heating element may have an internal short circuit or break.
The second most common problem is malfunction thermostat or a temperature sensor that controls the degree of heating of the liquid. If the thermostat contacts are oxidized or the sensor itself transmits incorrect data to the control module, the electronics “thinks” that the water is already hot and does not send a signal to turn on the heater. Some models Siemens and Hans The sensor is integrated into the flow-through heater, and its replacement requires disassembling the entire unit.
The third group of reasons is related to control module, which is the “brain” of the appliance. If the triacs or relays responsible for switching the heating element are burned out on the board, the heating command simply will not be executed, even if all other sensors are working. It is also worth considering the possibility of wiring breakage or oxidation of contacts in connectors, which often happens after leaks or vibration during long-term operation.
- 🔥 The nichrome spiral inside the heating element burned out due to a voltage surge or natural wear.
- 🌡️ Failure of the thermostat or NTC sensor, giving false readings about the water temperature.
- ⚡ Malfunction of the heating relay on the electronic control board or open circuit of the power supply.
- 🚰 Clogging of the circulation system, which prevents water from passing through the heating circuit.
⚠️ Attention: Before any diagnostics of the electrical part of the dishwasher, be sure to disconnect the device from the power supply. Working with 220V voltage in humid conditions is deadly.
Diagnostics of the heating element (heater)
Check heating element begins with its visual inspection after dismantling, although in most dishwashers it is hidden under the tank or built into the bottom of the washing chamber. There should be no blisters, thrones or through burns on the surface of the tube, however, even an ideal outer shell does not guarantee the serviceability of the internal spiral. For accurate diagnostics, you must use a multimeter set to resistance measurement mode (Ohm).
The normal resistance of a working heating element for dishwashers is usually from 20 to 40 Ohms, depending on the power of the element, which most often varies between 1.7–2.5 kW. If the multimeter shows one (infinity), it means there is a break in the circuit and the spiral has burned out, and if it is zero or a very low value, a short circuit has occurred. It is also critically important to check that there is no breakdown on the housing by touching one probe to the contact and the other to the metal tube of the heating element.
A common cause of heating element failure is the formation of a thick layer scale, which interferes with heat transfer. The heating element overheats inside the insulating layer of lime and burns out before it even has time to boil the water. Regular use of special water softeners and dishwasher cleaners helps extend the life of the heater by 2-3 times.
How to properly remove the heating element
Remove the lower basket and filters. Disconnect the power terminals (remember their location). Unscrew the fastening nuts or bolts holding the heating element. Carefully remove the element, being careful not to damage the rubber seal. When installing a new one, be sure to check the tightness of the rubber bands to avoid leaks.
- 🔧 Disconnect the machine from the network and remove the bottom panel or turn the device over (if the heating element is from below).
- 📏 Measure the resistance of the heating element: the norm is 20-40 Ohms, infinity means a break.
- 🚫 Check that there is no short circuit to the case (the resistance should be infinite).
- 🧼 Clean the seat from scale before installing a new element.
Checking the thermostat and temperature sensors
If the heating element is working properly, the next candidate for testing is thermostat or temperature sensor. Older models use mechanical thermostats, the principle of which is based on the expansion of a sensitive liquid or gas in a capillary when heated. When the set temperature is reached, the contacts open, breaking the power supply circuit of the heating element, and when it cools down, they close again.
In modern devices Candy, Gorenje and other brands are used electronic NTC sensors (thermistors), the resistance of which varies depending on the temperature of the environment. A malfunction of such a sensor often results in the control module receiving a signal that the water is supposedly already hot and does not turn on the heating, or, conversely, heats the water to a boil, which is dangerous.
Thermostat diagnostics involve “ringing” of contacts in a cold and heated state. When cold, the contacts of most thermostats should be closed (resistance close to zero). When heated (you can use a hairdryer or lower the sensitive element into hot water), a click should be heard and the chain should break. If there is no click or the contacts are stuck, the component must be replaced.
⚠️ Attention: Do not attempt to repair thermostats with sealed capillaries or damaged seals. Tightness is the main condition for their safe operation in an aquatic environment.
Control module and relay malfunctions
When all peripheral devices (heating elements, sensors) are working properly, the problem may lie in control module. The board contains electromagnetic relays that physically close and open the power circuit of the heating element at the command of the processor. Over time, the contacts inside the relay burn, stick, or oxidize, no longer passing the required current.
A burnt-out relay can be identified visually: traces of soot, melting or swelling often appear on the black plastic case. However, even an externally intact relay may have microcracks in the soldering or internal destruction of the contact group. To accurately test the relay, you need to apply voltage to its control coil and check the contacts with a multimeter.
Sometimes the reason for the lack of heating lies not in the relay itself, but in board tracks or triacs that control relays. If the board shows black marks, swollen capacitors, or signs of moisture, repairs may require professional re-soldering of components or replacement of the entire module. Self-repair of electronics without soldering and circuit design skills is not recommended.
When replacing a relay, select an analogue with identical parameters: coil voltage, maximum contact current and dimensions. Using a lower current relay will result in rapid re-combustion.
Influence of washing mode and program settings
Before disassembling the equipment, you should make sure that the correct one is selected washing mode. Many modern dishwashers have an “Eco” or “Quick 30 minutes” program, in which water heating is either not provided at all, or is carried out at low temperatures (30-40°C) to save energy and time. In such modes, the absence of a feeling of heat on the body or steam when opening the door is the norm and not a malfunction.
It's also worth checking your settings water softening (salinity). If the water hardness is set incorrectly, the machine may incorrectly calculate the heating time and temperature, although this less often leads to a complete lack of heating. Some models Miele or Asko have the function of connecting to hot water, and if the connection type is “Cold Water” in the settings, the machine will heat the water itself, and if “Hot” it will wait for warm water to arrive from the water supply.
The table below shows approximate heating temperatures for various modes so that you can figure out whether your machine heats up at all:
| Washing mode | Temperature (°C) | Process description |
|---|---|---|
| Pre-rinse | 15-25 (without heating) | Rinse off large food debris with cold water. |
| Eco / Economical | 45-50 | Long-term washing at moderate temperatures to save resources. |
| Intense / Heavy pollution | 65-70 | Maximum heat to remove dried-on grease and disinfect. |
| Auto mode | 45-65 (automatic) | The temperature depends on the degree of water contamination (turbidity sensor). |
If the machine is on Eco mode, the water may not feel hot, but it is enough to activate modern enzyme detergents.
Error Codes Indicating Heating Problems
Modern household appliances are equipped with a self-diagnosis system that displays error codes when malfunctions are detected. If the dishwasher does not heat water, it often signals this by flashing indicators or a combination of symbols. Deciphering the code allows you to immediately narrow down your search to a specific node.
For example, at Bosch and Siemens error E09 or flashing of the “S” (Salt) indicator often indicates problems with water heating or a malfunction of the heating element. U Electrolux and Zanussi code i30 or i60 may indicate that the water has not heated to the required temperature within the allotted time. Cars Indesit and Ariston the “Salt” indicator flashes frequently or shows a code C7, C03 in case of failure in the heater circuit.
Sometimes resetting the error (by unplugging the machine for 10-15 minutes) helps if there is a software failure, but if the problem is physical, the error will return during the next heating cycle.
☑️ Checklist for primary diagnostics
Frequently asked questions and answers (FAQ)
Is it possible to wash dishes in the dishwasher if it does not heat the water?
Technically, it is possible to run a washing cycle without heating, but the quality of washing will be extremely low. Fats will not dissolve, but will remain on the dishes and the inner walls of the machine, which will lead to the appearance of an unpleasant odor and the growth of bacteria. Additionally, the salt and rinse aid may not dissolve completely.
Why does the machine take too long to heat water?
Prolonged heating may indicate that the heating element is overgrown with scale, which impairs heat transfer, or a malfunction of the thermostat, which does not give a signal that the desired temperature has been reached. The cause may also be low voltage in the network or a malfunction of the control module.
How often do you need to change the heating element in a dishwasher?
The service life of the heating element depends on the water hardness and frequency of use. On average, when using water softeners and high-quality products, the heating element lasts 5-7 years. Without water softening, the service life can be reduced to 2-3 years due to overheating under the scale layer.
Is it safe to change the heating element yourself?
Replacing a heating element is a moderately complex procedure that requires basic skills in working with tools and a multimeter. The main safety condition is to completely disconnect the device from the power supply before starting work. If you are not confident in your abilities, it is better to consult a specialist.