Refrigerators Bosch are deservedly considered the standard of reliability, but even the highest quality equipment may require intervention over time. One of the common causes of temperature violations is the failure of the thermostat. This small element is responsible for turning the compressor on and off, maintaining the desired cold in the chambers.
If you notice that the refrigerator has stopped freezing or, conversely, turns food into ice, the problem may lie in this sensor. Thermostat is a mechanical or electronic “brain” that reads the temperature and gives a command to the motor. Understanding where exactly it is hidden in your model will be the first step to successful repair.
In modern models Bosch with a system No Frost and electronic control, the location of the sensors may differ from classic mechanical refrigerators. In the article we will analyze in detail the search algorithm, diagnostic methods and replacement nuances so that you can make an informed decision about repairs.
The operating principle and types of Bosch thermostats
Before looking for a part, it is important to understand what exactly we are dealing with. In refrigeration equipment of the brand Bosch historically two main types of regulators were used: mechanical capillary and electronic sensors (NTC thermistors). Mechanical thermostat is a sealed flask with gas or liquid that expands or contracts when the temperature changes, closing or opening electrical contacts.
Electronic sensors, which are more often found in modern models Series 6 and Series 8, work on the principle of changing resistance. They transmit digital data to the main control board. It is critically important to accurately determine the type of regulator you have before purchasing a replacement part, as they are not interchangeable. An error in selection will lead to incorrect operation of the entire cooling system.
Mechanical devices often have an adjustment screw that allows you to calibrate the temperature, while electronic ones require settings via the interface or replacement entirely. Understanding this difference will help you correctly interpret the symptoms of a malfunction.
Where the thermostat is located in different models
Localization of the thermostat directly depends on the design of your refrigerator Bosch. In classic two-chamber models with a drip defrosting system, the mechanical thermostat is most often hidden inside the refrigerator compartment. It can be found by removing the plastic cover from the inner wall or dismantling the temperature control unit, if it is located inside.
In units with a system No Frost the situation is more complicated. Here, temperature sensors (thermistors) are usually built into the evaporator or air ducts. Access to them often requires partial disassembly of the back wall of the refrigerator or freezer. In some models, the air temperature sensor is located in the upper part of the chamber, hidden by a decorative panel.
- 🔍 Classic models: under a plastic cover on the inner wall or in the control unit inside the chamber.
- ❄️ No Frost system: built into the evaporator behind the rear panel or in the cold supply duct.
- 📟 Electronic control: the sensor can be integrated into the display panel or hidden in the technical compartment.
If you have a model with a display on the door, the main air temperature sensor is often located in the upper part of the refrigerator compartment, next to the lamp or control unit. It is usually accessed by removing the top shelf and protective casing.
Diagnostics of thermostat malfunctions
Before disassembling the refrigerator, you need to make sure that the problem is in the thermostat. Symptoms may be similar to compressor malfunctions or freon leaks. The main sign of a thermostat failure is the lack of cyclical operation: the compressor either does not turn on at all or works without stopping.
For accurate diagnostics, you will need a multimeter. Contact testing is the most reliable way to check a mechanical thermostat. At room temperature, the contacts should be closed (unless it is a specific overheat shutdown sensor). When the sensor is cooled (for example, by putting it in the freezer for 15 minutes), the circuit should open.
⚠️ Attention: Carry out all work on diagnosing the electrical part only with the refrigerator disconnected from the network. Failure to comply with safety precautions may result in electric shock.
Electronic sensors are checked by measuring resistance. The values must correspond to the technical data sheet of the specific model Bosch. If the resistance tends to infinity or zero at normal temperature, the sensor is faulty.
☑️ Thermostat diagnostics
Instructions for replacing the thermostat
The replacement process requires accuracy and the availability of a basic set of tools: screwdrivers, pliers and possibly side cutters. If you decide that thermostat it is faulty, proceed step by step. First, dismantle all elements that interfere with access: shelves, drawers, decorative trims.
When working with a mechanical thermostat, pay special attention to the capillary tube. It is very thin and easily damaged. Do not bend or squeeze the tube, otherwise the new thermostat will also fail. Carefully remove the old flask from the seat, remembering the immersion depth.
Installing the new element is done in the reverse order. Make sure that the contacts are securely locked and that the tube is firmly attached to the evaporator or is in the correct position in the chamber. After assembly, do not rush to load products.
| Part type | Tools | Complexity | Replacement time |
|---|---|---|---|
| Mechanical thermostat | Screwdriver, pliers | Medium | 30-45 min |
| Electronic sensor (NTC) | Screwdriver, multimeter | High | 45-60 min |
| Thermostat with button | Screwdriver, side cutters | Low | 20-30 min |
What to do if the new thermostat does not fit the length of the tube?
If the capillary tube of the new thermostat is longer, carefully twist the excess into a ring (at least 3-4 cm in diameter) and place it in the free space behind the back wall. It is strictly forbidden to shorten the tube - this will disrupt the pressure in the system.
Adjustment and calibration after installation
After replacing the mechanical regulator, adjustment is often required. There may be an adjustment screw on the stem of the new thermostat. Turning clockwise usually increases the shutdown temperature (the compressor turns off earlier), counterclockwise - lowers it. However, the exact values depend on the specific batch of parts.
For refrigerators Bosch with electronic control, calibration can be carried out automatically after switching on, or require entering the service mode. In some cases, it is enough to simply pause for 5-10 minutes before connecting to the network so that the board “sees” the new sensor.
It is better to perform the first launch without loading products. Allow the unit to return to operating mode for 4-6 hours. Check the operation of the cycles: the motor should turn on when the temperature rises and turn off when the specified parameters are reached.
Typical mistakes in self-repair
DIY Repair is a risk, but it can be minimized by knowing about common mistakes. Often amateur DIYers forget to check the integrity of the door seals, believing that the problem is only in the thermostat. If the door is not airtight, even a working sensor will not be able to maintain the temperature, and the compressor will run constantly.
Another common mistake is ignoring the condition of the wiring. Oxidized contacts or frayed wires can give false readings or even break the circuit. Before installing a new thermostat, inspect the connectors and, if necessary, clean them.
⚠️ Attention: Do not use ordinary tape or low-quality electrical tape to insulate the wires inside the refrigerator. In the cold, the glue loses its properties and the material becomes tanned. Use only heat shrink or specialized insulation.
Also, do not forget that in modern models Bosch with inverter compressors, complex electronics are responsible for the operation of the cooling system. Replacing the sensor without resetting errors in the control board memory may not produce results.
When you should contact a professional
Despite the apparent simplicity, there are situations when it is better not to take risks. If your refrigerator is under warranty, any tampering will void the warranty. In this case, the only right solution is to call an official technician.
Also, the help of a professional is needed if after replacing the thermostat the problem does not go away. This may indicate a more serious problem: a refrigerant leak, a compressor failure, or a defect in the main control board. Diagnostics of these components requires special equipment.
Is it possible to temporarily operate a refrigerator with a faulty thermostat?
It is highly not recommended. If the thermostat is stuck on, the compressor will run continuously, causing it to overheat and burn out after a short time. If it does not turn on, the products will go bad.
Where to buy an original thermostat 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) from the nameplate.
Why a new thermostat does it click more often than the old one?
Frequent clicking may indicate incorrect calibration, a small difference in on/off temperatures (differential) or that the air circulation in the chamber is impaired (for example, drainage is clogged).
Does the temperature in the room affect the operation of the thermostat?
Yes, The thermostat responds to temperature differences. If the room is very cold (below +10°C), the refrigerator may not turn on, since the sensor “thinks” that it is cold enough inside. For such conditions, you need models with one compressor and a special valve.