A failure to heat water in a dishwasher is often accompanied by the appearance of a specific error code on the display or flashing indicators indicating a malfunction of the thermoregulation system. If the wash cycle goes through but the dishes remain cold and wet and the glass does not dry, this indicates that heating element does not receive power or is out of order. In modern models, electronics blocks the program from starting if the sensors detect no increase in temperature within a specified time.
The lack of hot water inside the chamber leads to poor dissolution of the detergent, especially if powder or tablets are used that require activation at temperatures above 45 degrees. Fatty stains are not broken down, a residue remains on the dishes, and an unpleasant smell of stagnant water may appear inside the device. Ignoring the problem may result in the machine endlessly trying to heat the water, wasting electricity, or, conversely, completing the cycle without disinfecting the appliances.
The first step in diagnosis is to exclude external factors, such as a closed hot water supply tap (if the model is connected to a hot water supply) or a malfunction of the surge protector. However, in 90% of cases when the dishwasher draws water but does not heat it, the problem lies in internal components: a burnt-out heating element, a stuck relay on the control board, or a faulty temperature sensor. Next, we will consider in detail each unit responsible for heat treatment and methods for checking them.
The main reasons for the lack of heating in dishwashers
The most common cause of heating system failure is failure heating element (tubular electric heater). Over time, scale forms on the surface of the tube, which impairs heat transfer, leading to local overheating of the nichrome spiral inside and its rupture. The cause may also be mechanical damage to the heater body or breakdown of insulation, which is often accompanied by knocking out of the machines in the panel when the washing mode is turned on.
The second most important factor is malfunction thermostat or temperature sensor (NTC). If this element transmits incorrect data to the control module that the water is already hot, although it is cold, the controller simply will not supply voltage to the heating element. Conversely, if the sensor is “closed” and shows a break, the system can go into emergency protection mode, blocking any heating processes to avoid a fire or damage to the plastic elements of the tank.
The third group of problems is related to electronic control board. On the printed circuit board there are power relays that switch the current to the heater. The contacts of these relays often burn out due to high currents and sparking, as a result of which the circuit is physically broken, even if the heating element itself is working. Microcracks in soldering or failure of triacs that control heating power in inverter models are also possible.
⚠️ Attention: Before any diagnostics inside the dishwasher body, be sure to disconnect the device from the power supply. Working with live electrical appliances is dangerous and can result in electric shock.
Technical nuances of the heating element’s operation
Inside the heating element there is a nichrome spiral enclosed in a metal tube filled with a dielectric filler (magnesium oxide). If the insulation breaks down, current can flow to the housing, which will trigger the RCD. The resistance test should show a value in the range of 20-40 Ohms, depending on the power of the model.
Diagnostics of the heating element and checking the resistance with a multimeter
To accurately determine the condition of the heating element, it is necessary to gain access to it, which in most models involves dismantling the bottom panel or completely removing the machine from the niche. Multimeter switches to resistance measurement mode (Ohms), and the probes are applied to the contacts of the heating element. The normal operating resistance of a working heater with a power of 1700-2000 W is approximately 25-35 Ohms. If the device shows one (infinity), it means that the spiral is broken and the element requires replacement.
It is also important to check that there is no breakdown in the housing. One multimeter probe is placed on the contact of the heating element, and the second on a metal flange or tube. The device should show infinite resistance. If the arrow deviates or a squeak is heard, it means that the insulation is broken, and operate such a heater strictly prohibited, since the water in the tank may be energized.
During a visual inspection, pay attention to the condition of the tube surface. The presence of bulges, deep holes or cracks indicates critical wear. Often the cause of burnout is dry work or excessive amounts of hard salts that create a heat-insulating crust. In such cases, even an electrically working coil may not transfer heat to the water effectively.
- 🔍 Turn off the power and remove the bottom heater access panel.
- ⚙️ Set the multimeter to resistance measurement mode (200 Ohm).
- 📏 Measure the resistance between the contacts of the heating element (the norm is 20-40 Ohms).
- ⚡ Check that there is no short circuit to the case (there should be one on the screen).
Malfunctions of the thermostat and temperature sensors
The temperature sensor in a dishwasher is usually a thermistor whose resistance changes depending on the temperature of the water. If the machine draws water, but does not heat, and the heating element is working properly, the problem may be that the “brains” of the machine receive a false signal about a high temperature. The test is carried out similarly to a heating element: the resistance of the sensor is measured at room temperature and compared with tabular data for a specific model Bosch, Electrolux or Candy.
Mechanical thermostats (capillary type) are found in older or budget models. They open the circuit when the set temperature is reached. If the contacts inside such a thermostat are burnt or oxidized, the circuit may not close at all, and the current simply will not reach the heater. Sometimes cleaning the contacts helps, but more often a complete replacement of the assembly is required, since the calibration of the mechanics is irreversibly disrupted.
In some designs, the sensor is built directly into the flow-through heater or located in the drain system. Its damage may be accompanied by water leakage if the seal of the seat is broken. When replacing, be sure to use heat-resistant sealants and original seals to avoid leaks on the floor.
When replacing the temperature sensor, lubricate the rubber O-ring with silicone grease. This will make installation easier and prevent premature aging of the rubber from high temperatures.
Problems with the control module and power relay
If all actuators (heating elements, sensors) are working properly, attention switches to control module. On the board, an electromagnetic relay is responsible for turning on the heater. With frequent switching under load, carbon deposits form on its contacts, increasing the contact resistance. Visually, this may look like a black spot on the relay body or on the board underneath it. In this case, the relay may click, but no contact will be made.
Repairing a board requires soldering and electronics skills. The faulty relay is unsoldered and replaced with a similar one with identical parameters (coil voltage, switching current). It is important to check the PCB traces for charring. If the currents have burned through the PCB, the conductive paths will need to be restored, otherwise the new relay will burn out in a short time.
In difficult cases, when not only the relay burns out, but also the control microcircuit or triac, repairs become economically impractical. Modern boards are often filled with compound or have a multilayer structure, which makes their restoration extremely labor-intensive. In such situations, owners often resort to purchasing a new module or installing a universal board (if technically possible).
The influence of scale and water hardness on heating
Hard water is the main enemy of heating elements. Calcium and magnesium salts are deposited on the heating element coils, forming a dense layer of scale. This layer has low thermal conductivity, which is why heat from the coil is poorly transferred to water. The heating element begins to heat itself, the temperature inside the tube rises to critical values, and the coil burns out. Even if the heating element is still intact, a layer of scale a few millimeters thick can double the water heating time.
For prevention it is necessary to use regularly water softener (special salt), pouring it into the compartment intended for this purpose. The water hardness setting in the dishwasher menu should correspond to the actual readings in your water supply. Ignoring this requirement leads not only to heating element breakdowns, but also to clogging of sprinkler nozzles and failure of heat exchangers (in models with heat recovery).
Heat Error Code Table
Different manufacturers use different fault coding systems. Below is a table with the most common codes indicating problems with water heating or circulation.
| Brand | Error code | Description of the problem | Probable Cause |
|---|---|---|---|
| Bosch / Siemens | E09 / E19 | Water heating problem | The heating element or sensor is faulty |
| Electrolux / Zanussi | i30 / i50 | Heating or circulation error | Filter clogged, heating element broken |
| Indesit / Ariston | H01 / H03 | Insufficient heating | Open circuit of heating element, relay |
| Candy / Hoover | E03 | Drain or heating problem | Blockage, pump/heater malfunction |
⚠️ Attention: Resetting the error using the buttons does not eliminate the physical breakdown. If the code appears again after a restart, it means that the faulty unit requires replacement.
Instructions for replacing the heating element
Replacing the heating element is a procedure that can be performed at home if you have a basic tool. First, you need to drain the remaining water from the machine by turning it over or tilting it. Then the bottom cover (or side, depending on the design) is removed and access to the bottom of the tank where the heater is fixed is opened.
The dismantling process involves disconnecting the wires (take a photo of the connection diagram first!), unscrewing the fastening nuts and carefully removing the element from the seat. When installing a new heating element, it is important to correctly position the sealing gasket and tighten the fasteners evenly to avoid distortion and leaks.
☑️ Checklist before assembly
After installation, reassemble the housing in reverse order, but do not place the machine in the niche yet. Run a short wash cycle without dishes and check that there are no leaks under the machine, and also make sure that the water begins to heat up (this can be checked by opening the door 10-15 minutes after the start of the wash - steam should come out of the chamber).
Main conclusion: In 80% of cases, the reason for the lack of heating is a burnt-out heating element or a stuck relay on the board. Replacing these elements restores the machine's functionality.
Prevention and service life extension
To prevent the “dishwasher not heating the water” problem from arising in the future, it is important to follow the operating instructions. Regularly clean the coarse filters at the bottom of the chamber from food debris, as their clogging disrupts circulation and can lead to local overheating of water near the heating element. Once every six months, it is recommended to run a cleaning cycle on the machine using a special product or citric acid to remove grease deposits.
Also keep an eye on the salt level in the container. Modern machines are able to regenerate the resin in the softener themselves, but without salt this process is impossible. If you live in a region with very hard water, it makes sense to install a main filter for mechanical and chemical cleaning at the entrance to the apartment, which will extend the life of not only the dishwasher, but also the washing machine and boiler.
FAQ: Frequently asked questions
Is it possible to wash dishes in the dishwasher if it does not heat the water?
Technically, the machine will perform cycles of dialing and draining, but the washing quality will be extremely poor. Cold water does not dissolve grease and does not activate most modern detergents. Additionally, missing a drying step (which often works through residual heat) will leave the dishes wet. Operation in this mode is only permissible temporarily.
Why does the dishwasher heat the water but not dry the dishes?
Drying often depends on a final rinse with hot water and a special chemical (rinse aid) to help the water drain. If the heating element is weak or the temperature sensor is acting up, the water may not reach the required temperature for effective condensation drying. Also check for rinse aid.
How much does it cost to replace a heating element at a service center?
The cost consists of the price of the spare part (from 1000 to 3000 rubles depending on the model) and the work of the specialist. On average, repairs will cost 3,000–6,000 rubles. Replacing it yourself will save on work, but requires tools and skills.
Can a power surge burn out a heating element?
Yes, sudden surges in voltage in the network can lead to overload and burnout of the nichrome spiral. Also, electronics (control board) often suffer from voltage surges, so it is recommended to connect the dishwasher through a stabilizer or at least a high-quality surge protector.