If you are faced with the fact that your refrigerator has stopped maintaining the set temperature regime or, conversely, has begun to freeze food, the cause is often a failure one of the components of the control system. In technical documentation and when ordering spare parts, you may come across a designation BS 1M, which to a non-specialist looks like a mysterious code. Understanding what is hidden behind this abbreviation is the first step to successfully repairing household appliances with your own hands.
This part is responsible for monitoring the temperature in various zones of the refrigerator compartment, transmitting signals to the main controller. It depends on its correct operation whether the compressor will turn on for cooling or stop when the required degrees are reached. In this article, we will analyze in detail the design of this element, consider typical malfunctions and give step-by-step instructions for diagnosing it.
Do not be intimidated by the technical jargon, since the design of this element is quite simple, and its replacement often does not require calling a technician. However, in order not to harm the remaining systems of the refrigeration unit, it is necessary to strictly follow the sequence of actions during dismantling and installation. We will help you figure out when replacement is really needed, and when the problem can be solved by adjustment.
What is hidden behind the BS 1M marking
The abbreviation BS 1M stands for “Bimetallic Stabilizer” or, in the broader context of refrigeration automation, a temperature control sensor with a bimetallic plate. The number “1” indicates the series or standard size of the device, and the letter “M” often indicates the modification or material of the contacts. This component is a key link in the temperature control chain, especially in refrigerator models where an accurate and quick response to changes in the thermal background is required.
The basis of the device is a bimetallic plate, which bends under the influence of heat and returns to its original position when cooled. This mechanical movement opens or closes electrical contacts, commanding the compressor to start or stop. In modern models, such sensors may have electronic “filling,” but the operating principle remains tied to the physical change in the properties of materials when heated.
⚠️ Attention: Do not confuse the BS 1M sensor with a conventional mechanical-type thermostat, which has an adjustment knob inside the chamber. BS 1M is most often a hidden element installed on the evaporator or in the air duct, and is not intended for frequent manual adjustment by the user.
It is important to understand that different manufacturers can use their own analogues of this part, but the functional purpose remains the same. When looking for a replacement, you need to pay attention not only to the markings, but also to the length of the capillary tube (if any) and the type of connection connector. Universal solutions exist, but they require adaptation of the seat.
Design features and principle of operation
The internal structure of the BS 1M sensor is a sealed system, protected from moisture and the aggressive environment inside the refrigerator. The main elements are the sensitive element, the contact group and the housing. The sensitive element reacts to the temperature of the surrounding air or the surface to which it is attached, providing measurement accuracy in the range necessary for the safety of products.
The operating principle is based on the difference in the linear expansion coefficients of two metals soldered together. When heated, one metal expands more than the other, causing the entire plate to bend. This bend pushes the rod or directly opens the contacts. In the model BS 1M this process is adjusted so that operation occurs at strictly defined values characteristic of the normal operation of the refrigeration unit.
Modern modifications may include additional protection elements, for example, overheating fuses that open the circuit completely at critical temperatures. This prevents compressor failure or wiring fires. Below is a table with the main technical characteristics characteristic of this type of sensors:
| Parameter | Value / Description | Impact on operation |
|---|---|---|
| Operating range | from -25°C to +15°C | Defines response zones |
| Calibration accuracy | ± 1.5°C | Influences temperature stability |
| Maximum current | up to 16 A | Contact load limit |
| Contact material | Silver / Nickel | Sparking resistance |
The tightness of the case plays a critical role, since condensation and moisture are constantly forming inside the refrigerator. If the seal is broken, water gets inside, causing corrosion of the contacts and false alarms. That is why, when installing a new part it is strictly not recommended damage the insulation of the wires or remove factory seals from the case, if this is not provided for by the design.
Typical symptoms of sensor malfunction
Determine that the BS 1M sensor has failed failure can be determined by a number of indirect signs that appear in the operation of the refrigerator. The most common symptom is incorrect temperature maintenance: food in the refrigerator compartment begins to deteriorate due to heat, or, conversely, freezes, turning into ice. This indicates that the signal about the current temperature is either not received or is distorted.
Another clear sign is the continuous operation of the compressor without shutting down. If the sensor is stuck in the “warm” position, the controller will constantly require cooling, which will lead to freezing of the rear wall and increased power consumption. In the opposite case, when the contacts do not close, the refrigerator may not turn on at all, leaving the inner chamber warm.
- ❄️ A “fur coat” or ice crust forms on the back wall of the refrigerator compartment, although the operating mode has not changed.
- 🔊 The compressor works at short intervals or, conversely, hums without interruption for several hours in a row.
- 💡 The indicators on the control panel blink or show an error related to the temperature regime.
- 🌡️ The actual temperature of the products does not correspond to the set values on the regulator.
Sometimes the malfunction can manifest itself chaotically: the refrigerator works normally for several days, and then suddenly stops cooling. This often indicates poor contact inside the sensor or oxidation of the terminals. In such cases, lightly tapping the refrigerator body can temporarily restore operation, but this only confirms the need to replace the part.
⚠️ Attention: If you notice that the compressor is running constantly, without delay, check the tightness of the door. Sometimes the problem lies not in the sensor, but in a cold leak, which is why a working sensor correctly requires continuous cooling.
Diagnostics and checking the serviceability of the part
Before going to the store for a new one spare part, you need to make sure that the problem lies in the BS 1M sensor, and not in the wiring or control board. To carry out diagnostics, you will need a multimeter set to resistance measurement mode (Ohms). This is a basic tool that any DIYer should have.
The first step is to unplug the refrigerator and gain access to the sensor. Depending on the model, it may be located behind a plastic panel inside the chamber or built into the evaporator housing. Carefully remove the protective covers, trying not to damage the plastic latches, which become brittle in the cold.
The test process is as follows:
- Disconnect the sensor connector from the electrical circuit.