A modern refrigerator Bosch is a complex electronic device where many sensors are responsible for maintaining an optimal climate. If you notice that the food in the main chamber has begun to freeze or, conversely, is quickly deteriorating, and an alarming error code appears on the display, most likely the problem lies in the temperature sensor. This small element, often called a thermistor, constantly transmits data to the control board, which, in turn, regulates the operation of the compressor.
Owners are often lost in search, since the location of the sensors differs depending on the defrosting system. In models with NoFrost there can be several sensors at once: in the evaporator, in the freezer and in the refrigerator compartment. In classic models with a “crying” wall, the design is simpler, but even there the element is hidden from the user’s eyes. Understanding the exact location thermostat is the first step to successful diagnosis without calling a technician.
In this article we will look in detail where exactly to look for the sensor in different series Bosch, how to check it correctly with a multimeter and whether it is worth trying to replace the part yourself. We will consider both visual signs of a malfunction and hardware testing methods.
The principle of operation and types of sensors in Bosch technology
The temperature sensor in refrigerators Bosch is a semiconductor resistor, the resistance of which changes depending on the heating or cooling of the environment. The main material is metal oxides, most often manganese and nickel. When the temperature drops, the resistance increases and the control board “understands” that the compressor needs to start. If the chamber is warm, the resistance drops and the unit goes into standby or defrost mode.
Modern models, such as Bosch Serie 6 or Serie 8, use digital sensors with high accuracy. They respond to temperature changes even in fractions of a degree. In older or budget models, analog thermostats may be found, but even there there are often additional electronic sensors for monitoring the evaporator. Thermistor This is the most common type of element that requires careful handling during dismantling.
There are several key control points:
- 🌡️ Air sensor: located in the upper part of the refrigerator compartment, measures the overall temperature.
- ❄️ Evaporator sensor: located in the freezer behind the back wall, controls the defrosting process.
- 🧊 Sensor in the “zero temperature” zone: found in models with MultiAirflow or VarioFresh.
Incorrect readings of any of these elements lead to chaotic operation of the compressor. For example, if the evaporator sensor “thinks” that there is no ice, it will not start the defrost heating element, which will lead to fouling with a “fur coat” and stopping air circulation.
Location of the sensor in refrigerators with the NoFrost system
In refrigerators Bosch with the system NoFrost searching for the sensor requires partial disassembly of the inside of the freezer. It is there, behind the plastic panel, that the evaporator and the main temperature control unit are hidden. Unlike static models, here the sensors are often mounted directly into the aluminum radiator fins or secured to plastic air duct clamps.
To get to the sensor, you need to remove all the freezer drawers and unscrew the mounting screws holding the back wall. Often the screws are hidden under decorative plugs. After removing the panel you will see the evaporator. The evaporator temperature sensor is usually mounted on one of the tubes or inserted into a special socket in an aluminum housing. It looks like a small cylinder in a plastic or metal case with two wires.
⚠️ Attention: Before removing the back panel in the freezer, be sure to unplug the refrigerator and let it stand for at least 12 hours. If you start disassembling right away, the ice on the evaporator may crumble and damage the thin freon pipes or the sensor itself.
An additional sensor that controls the temperature of the air leaving the freezer may be located at the outlet of the air duct. In some models Bosch it is integrated into the fan control unit. If you see a black plastic barrel with wires going to the board connector, this is the element you are looking for.
Searching for a temperature sensor in models with a drip system
In classic models Bosch with a drip defrosting system (where condensation appears on the back wall of the refrigerator compartment), the sensor is often built directly into wall or hidden behind a decorative trim. In such units, the main temperature control is carried out by a mechanical thermostat or an electronic sensor located in the ice formation zone on the rear panel.
The sensor is often hidden under a plastic cover at the top of the refrigerator compartment. To find it, you need to carefully remove the shelves and inspect the ceiling of the chamber. Sometimes access is possible by removing the lamp shade, as engineers Bosch often group electrical components in the upper area. The wires from the sensor go to the control unit, which in older models can be located in the base of the refrigerator, and in new ones - in the upper part.
Features of old Bosch models
In Bosch refrigerators produced before 2010, the temperature sensor could be combined with a power regulator. In such cases, replacement requires calibrating the entire assembly, and not just changing the thermistor.
If your refrigerator is equipped with a display on the door, but the defrosting system is drip, the sensor will still be electronic. Its wires can pass through the door hinge if the display is active, but the sensor itself is always located inside the camera. Look for a place where the plastic wall panel has a thickening or a technological hole closed with a plug.
Fault diagnosis: error codes and symptoms
Before disassembling the refrigerator, you should make sure that the problem is in the sensor. Refrigerators Bosch have a developed self-diagnosis system. If the sensor circuit is broken or short-circuited, the corresponding code lights up on the display. The most common errors are related to temperature sensors.
Below is a table of the main error codes indicating problems with temperature sensors in different series Bosch and Siemens (since the platforms are often identical):
| Error code | Value | Probable cause |
|---|---|---|
| E1 / F1 | Malfunction of the refrigerator compartment sensor | Open circuit or short circuit of the sensor |
| E2 / F2 | Malfunction of the freezer compartment sensor | Damage to the wiring or the thermistor itself |
| E3 / F3 | Evaporator sensor error | Problem with the NoFrost defrost sensor |
| E6 / F6 | Communication error | Problems with the board or connection sensors |
In addition to codes, malfunction thermistor is indicated by indirect signs. For example, the refrigerator runs non-stop, trying to reach the temperature, but cannot. Or the compressor does not turn on at all, although the chamber is warm. In NoFrost mode, a sign of a defrost sensor failure is the freezing of ice on the back wall of the freezer, which blocks the air supply channels.
A multimeter is required for accurate diagnosis. The sensor needs to be “ringed” for resistance. At room temperature, a working thermistor Bosch usually shows a resistance in the range from 2 to 5 kOhm (the exact value depends on the model and temperature). When cooling (for example, if you blow cold air on it with a hairdryer or apply ice), the resistance should gradually increase. If the device shows zero or infinity, the element is faulty.
Instructions for replacing the temperature sensor
Replacing the temperature sensor in the refrigerator Bosch is a procedure that requires care, but is accessible to a home craftsman. The main rule: never pull on the wires. They are very thin and easily break off at the very base of the sensor. All work is carried out only with the device de-energized.
The replacement process is as follows:
- 🔌 Disconnection: Unplug the power cord from the outlet. This is critical for safety and correct reset of board errors.
- 🛠️ Dismantling: Remove the necessary panels (the back wall of the freezer or the cover in the refrigerator compartment) according to the instructions described above.
- ✂️ Disconnection: Find the junction of the sensor wires with the main wiring. This is usually a connector or twist protected by heat shrink. Carefully separate them.
- 🆕 Installation: Install the new sensor in the same location. It is important to ensure tight contact with the surface that it must measure.
☑️ Check before assembly
If the wires of the new sensor are longer, they can be carefully laid in the free space, but do not wind them around the freon pipes - this may disrupt heat transfer. It is best to solder the wire connection and insulate it with heat-shrink tubing, since the twists oxidize under conditions of constant humidity and temperature changes.
After assembling all the panels, turn on the refrigerator. If the error on the display disappears and the unit begins to gain cold in normal mode, it means the replacement was successful. If the error code remains, perhaps the problem is not in the sensor, but in the wiring or the control board itself.
Common mistakes during self-repair
When trying to find and replace the sensor in the refrigerator Bosch beginners often make common mistakes that can aggravate the situation. One of the most common is the use of an inappropriate analogue. The sensors have different resistance characteristics (B-parameter), and installing a “similar” sensor from another brand will result in the refrigerator working incorrectly: either undercooling or overfreezing the food.
The second mistake is damage to the integrity of the wires during disassembly. The plastic in old refrigerators becomes brittle, and the sensor wires become very thin. Careless movement with a screwdriver can bite the wire. In this case, the wire will need to be extended, which creates additional points of potential failure.
⚠️ Warning: Do not use electrical tape to insulate connections inside the camera. Over time, the adhesive of the electrical tape flows, and the tape itself dries out. The only acceptable material is heat-shrink tube or specialized sealant for household appliances.
It is also a mistake to ignore checking other elements of the system. If the sensor burns out, it may be due to a power surge, which could also damage other components on the board. Blindly replacing the sensor without checking the circuit can lead to repeated failure in a short time.
Do not forget that in some models Bosch the sensor is embedded in polyurethane foam insulation of the case. In such cases, replacing it requires drilling out the insulation and subsequent professional foaming, which is practically impossible to do at home efficiently. If you find such a design, it is better to contact the service.
FAQ: Frequently asked questions
Is it possible to temporarily short-circuit the sensor to make the refrigerator work?
Technically, you can short-circuit the sensor by simulating a certain temperature, but this is extremely dangerous. The refrigerator will no longer understand the real temperature in the chamber and may either freeze all the food or, conversely, defrost. It can also lead to compressor failure due to improper cycling. Use this method only for short-term diagnostics, but not for operation.
Where to buy an original sensor for Bosch?
Original spare parts have an article number usually starting with 00 or 100.. (for example, 00623404). They can be found in authorized service centers Bosch or specialized stores of spare parts for household appliances. Analogues from Chinese manufacturers are cheaper, but their accuracy and durability often raise questions.
Why does the error not disappear after replacing the sensor?
The error may be stored in the memory of the control board. Try turning off the power to the refrigerator completely for 30-60 minutes. If this does not help, the new sensor itself may be faulty (defective), the wiring to the board is damaged, or the electronic control board itself has failed.
How much does it cost to replace the sensor in the service?
The cost consists of the price of the spare part and the work of the technician. On average, taking into account travel, this can cost 30-50% of the cost of a new budget refrigerator. Self-replacement saves money, but requires time and tools.