When malfunctions associated with temperature conditions occur in the operation of refrigeration equipment of a brand Bosch the first thing specialists do is pay attention to the control system. The central element here is a sensor that records the temperature on the radiator fins. Understanding exactly where it is located is a key step for carrying out high-quality diagnostics and subsequent repair of the unit.
In most modern models Bosch refrigerators this component is hidden from the user's eyes and requires partial disassembly of the freezer for access. Incorrect determination of the installation location can lead to damage to fragile plastic elements or loss of system tightness. That is why, before starting any manipulations, it is necessary to clearly understand the internal structure of your unit.
In this article we will analyze in detail the design of the evaporation unit, indicate the exact coordinates of the location of the sensor in various series of equipment and describe the signs indicating its failure. You will learn how to safely get to the desired part and what to pay special attention to during the inspection process.
Design features of the No Frost system in Bosch
Refrigerators Boschequipped with the system No Frosthave a complex air circulation architecture. Unlike a drip system, where cooling occurs due to natural convection, here the air is forced by a fan through the evaporator. The sensor in question is attached directly to the lamellas of this heat exchanger in order to monitor in real time the degree of freezing.
The location of the evaporator in the German brand's technology is traditionally located at the back of the freezer. It is hidden behind a plastic panel, which serves as an air duct and protection from mechanical damage. The temperature sensor (thermistor) is usually mounted in a special groove on the evaporator tubes or pressed tightly against them with a metal bracket to ensure ideal thermal contact.
It is important to understand that in two-chamber models with one compressor, the evaporator is often common, but there may be several sensors. One is responsible for the defrost cycle, the other can control the temperature of the air leaving the evaporator. Thermostat and the electronic sensor are different things, although their functions are similar, but the operating principle is radically different.
- 🔍 The sensor usually has a black or white plastic tip into which it is sealed sensitive element.
- ❄️ Fastening is carried out either by snapping into the evaporator body, or by a tight fit through heat-conducting paste.
- 🔌 The wires from the sensor go directly to the electronic control module, often passing through the corrugated protection.
The exact location of the sensor: step-by-step access instructions
To get to the place where it is defrost sensor, you will need to perform a series of sequential actions. First, completely defrost the chamber if there is ice in it, as the presence of ice will make it difficult to remove the panel. Then remove all shelves, drawers and baskets from the freezer compartment, freeing access to the back wall.
The back panel is secured with screws or plastic clips. Models Bosch Serie 4 and Serie 6 often use screws hidden under decorative plugs or located inside niches for fastening shelves. After unscrewing the fasteners, the panel is carefully moved to the side. Be careful: wiring for a fan or light bulb may be attached to it.
Behind the removed panel you will see an aluminum evaporator radiator. The temperature sensor in refrigerators Bosch is most often located in the upper right or left part of the coil. It looks like a small cylinder inserted into the hole between the radiator fins. In some modifications, it can be attached to the freon outlet tube immediately after exiting the evaporator.
☑️ Algorithm for accessing the sensor
Visually determine the malfunction of the sensor itself difficult, it has no external signs of damage unless the wires are broken. However, if a massive “coat” of ice is visible on the evaporator, and the fan hums but does not blow, this may indicate that the defrost system does not start due to incorrect sensor readings.
Differences in location for different series of refrigerators
Engineering solutions of the company Bosch vary from series to series to the series, which affects the layout of internal components. In older models with mechanical control, the sensor could be placed on the visible part of the body, but in modern lines hidden installation prevails. This is done to protect against moisture and mechanical stress when loading products.
The series Bosch VitaFresh often uses a double control system. One sensor is responsible for the temperature in the chamber, and the second, the same one on the evaporator, regulates the defrost cycles. Their location may differ by a few centimeters, but both are in the low temperature zone behind the back wall. An error when replacing one with another will lead to incorrect operation of the units.
Built-in models have their own layout features due to the limited space of the case. Access to the rear panel may be difficult if the refrigerator is installed in a niche. In such cases, it is sometimes necessary to move the entire cabinet or remove the top cover of the device to access the upper fastenings of the evaporator panel.
⚠️ Attention: In some modifications of Bosch refrigerators, the sensor is fixed with a heat-shrinkable tube or special sealant. Do not cut it with a knife, as this may damage the sensitive element. Use a hair dryer to gently soften the fixation.
It is difficult to remove the back panel
I can’t find the sensor itself
The wires are mixed up
The panel is cracked when removal-->
Symptoms of a malfunctioning temperature sensor
Understanding where the element is located is useless without the ability to diagnose its failure. If thermistor fails, the refrigerator stops receiving correct data about the evaporator temperature. This results in the defrost timer not working on time, or, conversely, the defrost starting too often, preventing the cold from building up.
The first sign of a problem is the formation of a giant layer of ice on the back wall of the freezer, which can block the fan. As a result, the cold stops flowing into the refrigerator compartment, and the food in the main chamber begins to deteriorate, although the freezer can work in enhanced mode. The electronics detects the error and can display a code on the display.
Frequent errors associated with the evaporator sensor in technology Boschare displayed as combinations on the indicators. For example, the temperature indicator blinks or a code appears E03, E06 or F03 (coding depends on the specific model and year of manufacture). These signals indicate an open circuit or short circuit in the sensor circuit.
| Symptom | Probable cause | Action |
|---|---|---|
| Ice coat on the evaporator | The sensor does not detect heating and does not turn on the heating element | Replacing the sensor |
| The refrigerator does not freeze | The fan is blocked by ice | Defrosting and checking the sensor |
| Error code on the display | Open circuit of the thermistor | Dial with a multimeter |
| Continuous operation of the compressor | Incorrect temperature readings | Electronics diagnostics |
Why can a sensor lie?
Over time, the internal resistance of the thermistor changes. Even if it is physically intact, its readings may shift by 5-10 degrees, which confuses the controller’s operating algorithms.
The process of replacing and checking resistance
To check the serviceability of the element is necessary multimeter. The sensor is removed from the seat (having previously disconnected the connector chip) and checked for resistance. At room temperature, a working sensor Bosch usually shows a resistance in the range from 4 to 6 kOhm, but the exact values depend on the model.
If, when the sensor is heated in the hands, the resistance does not change or shows infinity (break), the part must be replaced. Installing a new element requires observing polarity if the connector is not symmetrical, although this is often not critical for thermistors. The main thing is to ensure tight contact with the surface of the evaporator.
When installing a new sensor in refrigerators Bosch it is recommended to use a special heat-conducting lubricant, if provided for by the design. This will improve the speed of the sensor's response to temperature changes. After assembling the entire structure and connecting it to the network, the defrost cycle should start automatically or after resetting the error.
⚠️ Attention: Never use ordinary glue or electrical tape to attach the sensor. These materials are heat insulators and will lead to a delay in readings, which will again cause the system to freeze.
Common mistakes during self-repair
Independent repair of refrigeration equipment is fraught with risks. One of the common mistakes is damage to the evaporator tubes when removing the panel carelessly or trying to pry off a frozen sensor. Aluminum is very soft, and a puncture of the tube will lead to the release of freon and expensive repairs by a technician.
Another mistake is ignoring the wiring check. Often it is not the sensor itself that breaks, but the wire at the entrance to the camera or in the door hinge (if the sensor is placed there) is broken. Before purchasing a new part, be sure to ring the circuit to the control module connector.
Also, users often confuse the defrost sensor and the air temperature sensor. They may look the same, but have different temperature characteristics. Installing an unsuitable element will result in the refrigerator not working correctly, even if formally everything is connected correctly.
Is it possible to operate a refrigerator with a faulty sensor?
Short-term operation is possible, but this will lead to ice build-up, fan failure and increased power consumption. The compressor will work for wear, trying to compensate for the lack of cold.
Where to buy an original sensor for Bosch?
It is better to purchase original spare parts from authorized service centers or specialized stores of spare parts for household appliances, indicating the exact model number (E-Nr) of your refrigerator.
How much How long does it take to replace the sensor?
An experienced technician needs about 30-40 minutes, including defrosting. Self-replacement for an inexperienced user can take up to 2 hours, including time for cooling of the plastic and careful assembly.
Why does the error not disappear after replacing the sensor?
In some models Bosch requires resetting the error through the menu or completely turning off the power for a long time (more than 1 hour) for the controller to overwritten data about the malfunction.