No water heating in the dishwasher Bosch leads to the fact that the dishes remain dirty, and the fat does not dissolve even when using high-quality detergents. Most often the problem lies in a burnt out Heating element, a malfunction of the water flow sensor or a malfunction in the control module, which stops supplying voltage to the heating element. In some cases, the equipment continues the washing cycle, but the result is disastrous, since the water remains cold, which is especially critical for modes with high temperatures.
Diagnostics must begin by checking the error codes that are displayed on the display or indicated by flashing lights. If the car Bosch does not heat the water, but continues to work, this often indicates a breakdown of the heater itself or an open circuit, while a complete failure to start the wash cycle may indicate problems with the water supply or blockage from the electronics. It is important to understand that modern models are equipped with a complex self-diagnosis system, which can limit the operation of the unit at the slightest suspicion of danger.
The main reasons for the lack of water heating
There are several key factors due to which dishwasher stops increasing the temperature of the liquid. The most common reason is failure of the tubular electric heater. Scale accumulating on the surface of the spirals leads to local overheating and rupture of the nichrome thread. It is difficult to visually determine such a breakdown, so a test with a multimeter is required. If the resistance tends to infinity, the part must be replaced.
The second important element is flow sensor (aquacontrol). If it does not detect the movement of water or gives erroneous readings, the controller simply will not give a command to turn on the heating element in order to avoid dry running. There are also often problems with the thermostat or temperature sensor, which can “lie” to the control module, reporting that the water is already hot, although in fact it is cold. In this case, the cycle will proceed without heating.
- 🔥 Burnout of heating element spirals due to voltage surges or scale.
- 🌊 Malfunction of the flow sensor blocking the heating start.
- ❄️ Oxidation of contacts on the heating element terminals or broken wiring.
- 🧠 Malfunction of the electronic control module (burnt relay).
⚠️ Attention: Before starting any diagnostic work, be sure to turn off the dishwasher Bosch from the electrical network. Working with live electrical appliances is deadly.
How to check a heating element with a multimeter
To check the heater, you need to gain access to it (usually located at the bottom of the washing chamber). Remove the terminals, switch the multimeter to resistance measurement mode (Ohm) and touch the probes to the contacts of the heating element. A working element will show a resistance in the range of 20–40 ohms. If the device shows one or zero, the element is faulty. Also check the breakdown on the body: one probe on the contact, the other on the metal tube of the heating element. Resistance must be endless.
Diagnosis of errors and fault codes
Modern models Bosch (series SMV, SPV, SMS) display information about faults through flashing indicators or a digital display. Code E09 (or the blinking of the drying indicator) most often indicates heating problems. This could be a malfunction of the heating element, thermostat, or even just low voltage in the network. If the machine shows this code, it can interrupt the program or continue washing with cold water, notifying the user of the problem.
Sometimes the error is not clearly displayed, but the machine behaves strangely: the cycle takes longer than usual because the controller is trying to heat the water, but does not receive confirmation from the temperature sensor. In such cases, it is useful to run the self-diagnosis mode. To do this, on many models you need to hold down a certain combination of buttons (for example, the program selection button and the power button) for several seconds. The system will test the nodes and issue the current error code.
External factors should also be taken into account. If lukewarm water flows from the tap, the machine will take much longer to heat up to the required temperature. 60-70°C. However, if the water from the tap is hot and the water in the car is cold, the problem is definitely inside the device. The selected program also affects the heating: in the “Eco” or “Quick Wash” mode, the temperature may be lower, and the user will mistakenly consider this a breakdown.
Checking the heating element and power circuit
For a detailed inspection, it is necessary to remove the bottom panel of the dishwasher Bosch. The heating element is usually located under the filter or on the side at the bottom of the tank. Visually inspect the part: there should be no swelling, cracks or heavy scale deposits on it, although the latter does not always mean a breakdown. Pay special attention to the contact group: often the terminals oxidize or melt, which breaks contact.
If a visual inspection reveals no defects, proceed to electrical measurements. In addition to the resistance of the heating element itself, it is important to check the integrity of the supply wires. Test the circuit from the connector on the control module to the heater contacts. A break in the wiring is a common reason why heating does not turn on, even if the element itself is working. Use your model diagram to determine the exact wire colors.
| Validation parameter | Normal value | Symptom of malfunction | Action |
|---|---|---|---|
| Heating element resistance | 20–40 Ohm | Infinity or 0 Ohm | Replacing the heating element |
| Breakdown to the body | Infinity | Any resistance value | Replacing the heating element (dangerous!) |
| Wire integrity | 0 Ohm (there is a bell) | Infinity (break) | Chain recovery |
| Input voltage | 220–230 Volt | No voltage | Module/relay check |
⚠️ Attention: If a breakdown of the heating element is detected on the body, further operation of the machine is prohibited. This can lead to electric shock through water and dishes, as well as tripping the RCD in the panel.
Malfunctions of sensors and the AquaSensor system
In dishwashers Bosch frequently used system AquaSensor, which determines the transparency of the water and adjusts the washing cycle. If this sensor is dirty or faulty, it may send incorrect data to the processor. Although it is not directly responsible for heating, its readings indirectly affect the logic of the program. For example, if the system “thinks” that the water is too dirty, it can extend the rinse cycle, but if there is an error in the temperature sensor, the heating will not turn on at all.
The flow meter deserves special attention. This device controls the volume of incoming water. If the sensor impeller is jammed or the magnet that senses rotation is loose, the control module will not receive a signal to fill the tank. Without this signal, the switching command heating element will not be shipped for security reasons. Cleaning the flow sensor can sometimes solve the problem if debris or broken glass has gotten into it.
The thermostat (or NTC sensor) is another critical component. It measures water temperature in real time. If its readings “fly” towards high values (for example, it shows 80°C when it really is 20°C), the control module will decide that the water is already hot and will not turn on the heating. This element is also checked with a multimeter: as the temperature changes, its resistance should change smoothly.
☑️ Checklist for checking sensors
Problems with the control module and relays
If all actuators (heating elements, sensors) are working properly, the problem may lie in the “brains” of the machine - the control module. Inside it is a relay that physically closes the heater's power circuit. Over time, the relay contacts burn out or stick, and current stops flowing to heating element. This is a common problem with cars. Bosch over 5-7 years old.
Diagnostics of the module requires opening the case and visually inspecting the board. Look for blackening in the area of the heating element relay, swollen capacitors or traces of water ingress. If there are no visual defects, but voltage does not appear at the output terminals of the relay at the moment when heating should occur, then the relay is faulty. It can be re-soldered if you have the skills to work with a soldering iron, or you can replace the entire module.
Sometimes the failure is software in nature. In this case, resetting the settings to factory settings or rebooting the machine may help. To do this, you usually need to hold the “Start” button or a special combination for 3-5 seconds. However, if the problem is hardware (burnt out part), a soft reset will not help.
⚠️ Attention: Repairing the control module requires high qualifications. Inept intervention can lead to a short circuit and failure of all electronics of the dishwasher.
Main conclusion: If the heating element and wiring are intact, but there is no voltage on them, in 90% of cases the relay on the control board or the sensor blocking the start is to blame.
The effects of hard water and prevention
Hard water is the main enemy of heating elements. Calcium and magnesium salts settle on the heating element coils, forming a hard layer of scale. This layer has low thermal conductivity, which is why the heating element overheats inside the scale layer and quickly burns out. In addition, scale may isolate the temperature sensor, causing it to read data incorrectly. Regular use of salt softener and special all-in-1 tablets significantly extends the life of the machine Bosch.
For prevention, it is recommended to clean the machine from scale and grease every 3-6 months. There are special cleaning products for dishwashers that run on an idle cycle at high temperatures. It is also useful to check and clean the coarse filters at the water inlet to prevent debris from getting inside the system and jamming the sensors.
If you live in an area with very hard water, it makes sense to install a magnetic or polyphosphate filter on the inlet pipe in front of the machine. This will reduce the load on the built-in softener and protect heating element from rapid fouling. Remember that saving on dishwasher salt often leads to expensive repairs after a year or two of use.
Tip: You can use special test strips to check water hardness. If the hardness is above 10°dH, the use of regenerating salt is mandatory, even if you use 3 in 1 tablets.
When you need to call a specialist
Self-repair is possible if you have basic skills in working with tools and a multimeter, and the problem is obvious (for example, a heating element has burned out). However, if you need to replace the control module, resolder relays, or complex electronic diagnostics, it is better to turn to professionals. Incorrect assembly or incorrect diagnosis can aggravate the situation and lead to a leak or fire.
Also, the help of a specialist is needed if the car is under warranty. Opening the seals on your own automatically voids the manufacturer's warranty. In this case, any repairs should be carried out only by an authorized service center Bosch.
FAQ: Frequently asked questions
Why does my Bosch dishwasher heat the water, but not completely?
This may be caused by a malfunction of the heating element (partial breakdown), incorrect operation of the temperature sensor, or too low incoming water temperature. It is also possible that the filter is clogged or there are problems with the circulation pump.
Is it possible to wash dishes if the machine does not heat the water?
Technically, the machine will work, but the quality of the wash will be extremely low. Fats will not dissolve and bacteria will not die. In addition, some detergent tablets are only activated at temperatures above 45-50°C.
How much does it cost to replace the heating element in a Bosch dishwasher?
The cost consists of the price of the part (usually from 1,500 to 4,000 rubles depending on the model) and the cost of the craftsman’s work. Replacing it yourself is cheaper, but requires time and tools.
How to reset error E09 on a Bosch dishwasher?
Try turning off the machine with the button, then unplugging the plug from the socket for 15-20 minutes. If the error remains after switching on again, it means that the malfunction has not gone away and requires elimination.
Why are the dishes wet after washing if the machine does not heat?
In cars Bosch drying is often condensation and depends on the temperature of the tank walls, which heat up at the end of the cycle. If there was no heating, the walls are cold, condensation does not settle, and the dishes remain wet.