Modern refrigerators Bosch are complex electronic systems where the accuracy of climate control depends on many sensors. If you notice that the equipment begins to work incorrectly, the food freezes slightly or, conversely, spoils too quickly, the problem often lies in temperature sensors. These small elements continuously transmit signals to the control module, regulating the operation of the compressor and fans.
Understanding the principle of operation and the ability to carry out basic diagnostics will help you avoid an expensive call to the technician in cases where the breakdown is minor. In this article, we will analyze in detail how to identify a malfunction, what tools are needed and what to pay attention to when analyzing the readings.
Do not panic if an alarm indicator lights up on the display. Often timely checking and replacement of one inexpensive element returns the unit to full functionality. It is important to act consistently and observe electrical safety measures.
Symptoms of thermal sensor malfunction
The first sign that temperature sensors has failed is the incorrect behavior of the refrigerator compartment. The unit may hum continuously without turning off, trying to reach impossible temperature values. Or, on the contrary, the compressor will turn on too rarely, which will lead to defrosting of the contents.
Pay attention to the following alarm signals:
- ❄️ A “coat” of ice or condensation forms on the walls of the chamber, although the operating mode has not changed.
- 🔊 The compressor runs without interruption or turns on too often (clocking).
- 🌡️ The actual temperature inside the chambers is very different from the one set on the display.
- 💡 Indicators flash on the control panel or error codes are displayed (for example, E03, E05).
Often users ignore these symptoms, considering them a temporary failure. However faulty sensor forces the electronics to operate in emergency mode, which significantly reduces the life of an expensive compressor. If you find at least one of the listed signs, you need to carry out an in-depth diagnosis.
⚠️ Attention: Operating a refrigerator with a faulty sensor can lead to spoilage of a large number of products and failure of the compressor due to overload.
Types of sensors in Bosch refrigerators
B Refrigerator designs Bosch use several types of sensors, each of which is responsible for its own section of the system. Understanding their location and purpose is the key to a successful renovation. The main element is NTC thermistor, the resistance of which varies depending on the ambient temperature.
The main types of sensors installed in modern models:
- 📍 Evaporator sensor: controls the temperature of the cooling element, preventing icing or overheating.
- 📍 Refrigeration chamber sensor: located on the rear wall, regulates the motor switching cycles.
- 📍 Freezer chamber sensor: monitors the deep freezing mode.
- 📍 No Frost sensor: participates in controlling the defrost system.
Each of these elements has its own technical characteristics and resistance range. For example, a standard sensor at room temperature may have a resistance of about 5 kOhm, and at -18°C - more than 30 kOhm. Knowledge of these parameters is necessary for an accurate check.
In models with a system MultiAirflow or VarioZone the number of sensors can be increased for more accurate zoning of space. In such cases, diagnostics require checking each element separately, since the failure of one sensor can upset the balance in the entire system.
What is an NTC thermistor?
NTC (Negative Temperature Coefficient) is a semiconductor resistor whose resistance decreases as the temperature rises. It is this principle that underlies the operation of most sensors in Bosch household appliances.
Necessary tools for diagnostics
To carry out a quality test, you will need a minimum set of tools. Without specialized equipment, it is almost impossible to carry out accurate diagnostics, since a visual inspection rarely gives results - a burnt sensor often looks the same as a working one.
The master's basic kit includes:
- 🛠️ Multimeter (tester): required for measuring resistance and checking the circuit for open circuit.
- 🛠️ Set of screwdrivers: for dismantling panels and removing protective covers.
- 🛠️ Container with ice and hot water: to check the sensor's response to temperature changes.
- 🛠️ Technical hair dryer: (optional) to speed up heating sensor.
Particular attention should be paid to the multimeter. It must be in working order and have charged batteries. Before starting work, make sure that the device is switched to resistance measurement mode (Ohm) and the correct range is selected, usually 20 kOhm or 200 kOhm.
It is also a good idea to prepare a notepad for recording the readings. Record the resistance values at different temperatures so you can compare them with the tabulated data later. This will help avoid confusion if you are testing several sensors at the same time.
Testing procedure with a multimeter
The most reliable way to check temperature sensor is to measure its electrical resistance. To do this, you need to gain access to the sensor, which often requires partial disassembly of the refrigerator. Before starting any work, be sure to disconnect the unit from the power supply!
The step-by-step algorithm of actions is as follows:
- Dismantle the required panel or remove the lampshade to get to the sensor.
- Carefully disconnect the connector sensor from the wiring harness.
- Connect the multimeter probes to the sensor contacts.
- Fix the resistance reading at room temperature.
- Place the sensor in a container of water of known temperature (or apply it to ice) and monitor the change in readings.
A working sensor should smoothly change resistance as the temperature changes. If the multimeter shows one (infinity) or zero, this indicates open circuit or a short circuit, respectively. In both cases, the element must be replaced.
Normal resistance at +25°C: 4.7 - 5.5 kOhm
Normal resistance at 0°C: 15 - 17 kOhm
It is important to check not only the sensor itself, but also the integrity of the supply wires. Often the fracture occurs at the very base or at the exit point from the body. Ring the wires from the connector to the sensor itself to eliminate this malfunction.
☑️ Check algorithm
⚠️ Attention: Do not try to test the sensor while it is connected to the control board. You will receive incorrect readings due to the influence of other circuit elements.
Resistance and temperature correspondence table
For accurate diagnostics, you need to know the reference values. Although the parameters may vary slightly in different series Bosch, the general dependence of resistance on temperature remains unchanged for most NTC thermistors used in this technique.
Below is a table that will help you determine the health of the element:
| Temperature (°C) | Resistance (kOhm) | Permissible error | Condition |
|---|---|---|---|
| +25 | 5.0 | ± 5% | Normal |
| +10 | 8.5 | ± 10% | Normal |
| 0 | 16.0 | ± 10% | Normal |
| -18 | 33.0 | ± 15% | Normal |
| Any | 0 or ∞ | 0% | Faulty |
If your measurements are radically different from given data, for example, at room temperature the device shows 20 kOhm or 1 kOhm, which means it is broken. Such an element will transmit distorted signals to the module, causing the refrigerator to operate incorrectly. sensor characteristics broken. Such an element will transmit distorted signals to the module, causing the refrigerator to operate incorrectly.
It is worth considering that at very low or very high temperatures, the measurement error may increase. Therefore, checking at two points is considered the most informative: at room temperature and at a temperature of about 0°C (melting ice).
Error codes and their interpretation
Modern refrigerators Bosch are equipped with a self-diagnosis system that displays information about faults on the display in the form of codes. This greatly simplifies the search for the problem, pointing directly to the unit that requires attention.
The most common codes associated with temperature sensors:
- 🚫 E01 / E02: Faulty refrigerator compartment sensor (open or shorted).
- 🚫 E03 / E04: Problems with the freezer sensor.
- 🚫 E05 / E06: Error in the evaporator sensor or No Frost system.
- 🚫 E11: Failure of communication between modules (may be caused by oxidation of the sensor contacts).
The presence of an error code does not always mean that the sensor itself has burned out. Often the problem lies in oxidized contacts, frayed wires or a faulty control board. Therefore, a visual inspection and “continuity” of the circuit are required even if there is a clear code.
Sometimes after replacing the sensor, the error does not disappear immediately. In such cases, you may need to reset the error through the settings menu or completely disconnect the refrigerator from the network for 15-20 minutes. This will allow the controller to reboot and take new readings.
Frequently asked questions (FAQ)
Is it possible to install a universal sensor instead of the original Bosch?
Technically this is possible if the resistance and dimensions match. However, original sensors have a specific resistance versus temperature curve. Installing a universal analogue can lead to errors in operation, so it is better to look for an original article or a proven analogue.
Why does the refrigerator freeze but does not turn off?
Most likely, the temperature sensor is “stuck” or shows incorrect data, telling the module that it is warm in the chamber. Because of this, the compressor runs continuously. It is necessary to check the sensor in the refrigerator compartment.
How often do you need to change temperature sensors?
Sensors do not have a specific service life; they are replaced when they fail. However, over time (after 7-10 years), their characteristics may “float”, which leads to less accurate operation of the refrigerator.
Does humidity affect the operation of the sensor?
Yes, moisture getting into the connector or contacts can cause a short circuit or corrosion, which will lead to errors. When replacing the sensor, always check the condition of the insulation and the tightness of the connections.
What to do if the error remains after replacing the sensor?
It is necessary to reset the error in the module memory. Try unplugging the refrigerator for 20 minutes. If this does not help, check the integrity of the wiring from the connector to the control board.