For most owners of refrigeration equipment, the question of where the thermostat is located and what exactly it looks like becomes relevant only at the moment of breakdown. This small component does a tremendous job: it reads the temperature inside the chambers and sends signals to the compressor to turn on or off. Understanding its appearance and operating principle will help you quickly diagnose the problem or replace the failed part yourself.
Externally, these devices can vary greatly depending on the year of manufacture of the refrigerator, its brand and the type of control system. If in older models you find a mechanical unit with a long tube, then in modern units it may be a tiny electronic sensor hidden deep in the wall. Thermostat is the heart of the cooling system, and its visual identification is the first step to repair.
In this article we will look in detail at what the different ones look like types of regulators, where to look for them and how they differ from each other. You will learn what markings to pay attention to and why the external similarity of parts does not always mean they are completely interchangeable.
Mechanical thermostat: classic design
The most common type that can be found in middle-aged refrigerators (for example, Atlant, Biryusaold Indesit), is a mechanical thermostat. Externally, it is a small rectangular or square plastic case, usually black or white. The dimensions of such a block rarely exceed the dimensions of a matchbox, although larger modifications are also found.
The main visual distinctive feature of the mechanics is the long capillary tube, which extends from the body. This thin copper tube, often enclosed in an additional protective sheath, can range from 0.5 to 3 meters in length. It is this that is inserted into the evaporator or attached to the chamber wall in order to sense temperature changes. At the end of the tube there is a sensitive element - a bellows, which expands or contracts when heated or cooled.
On the body of the device there is always a rotating rod on which the temperature control knob is placed. Depending on the model of the refrigerator, this knob can be:
- 🌀 A plastic disk with numbers from 1 to 7 or Min/Max.
- 🔘 A metal rod with a slot for a flat-head screwdriver (found in hidden regulators).
- 🎚️ A slider moving along the scale.
⚠️ Attention: The capillary tube of a mechanical thermostat is filled with freon or inert gas under pressure. It is strictly forbidden to bite, bend at an acute angle or pierce this tube. Damage to the seal will lead to immediate loss of functionality of the sensor.
In addition to the tube and rod, you will see electrical terminals on the body. There may be two or three. If there are three terminals, then the third is usually used to connect a light indicating the operation of the compressor. When replacing, it is important to remember or photograph which wire was connected to which terminal, since the colors of the wire insulation do not always correspond to the standard.
Electronic temperature sensors (thermistors)
In modern refrigerators with a system No Frost and electronic control (brands Samsung, LG, Bosch) you will not find the usual block with a tube. Electronic sensors are used here - thermistors. Visually, they are a small plastic or metal tip, often similar to a bullet or cylinder with a diameter of 5-10 mm.
A pair of thin wires come from this tip, combined into a common cable. The length of such a loop is usually short, since the sensors are located directly in the cooled areas or in the air flow. The sensor housing can be made of stainless steel, copper or heat-resistant plastic. Unlike mechanics, there are no moving parts or gas-filled tubes.
In refrigerators with a system No Frost several of these sensors are often installed at different points:
- ❄️ In the evaporator (to control the defrosting process).
- 🌬️ In the air duct (to control the temperature of the air supplied to the chamber).
- 🥩 In the main chamber (for precise climate control).
Externally, these sensors can be very similar, but have different internal resistance. Therefore, when performing a visual replacement, it is important to pay attention to the markings or part number stamped on the housing or indicated on the wiring harness tag. Replacement "by eye" can lead to incorrect operation of the refrigerator, even if the sensor is physically in place.
Where to look for a thermostat: main installation locations
Finding a thermostat depends on the design of your refrigerator. In older models with a single chamber and an open evaporator ("crying" wall), the thermostat is often located inside the refrigerator compartment. Its body can be recessed into the wall, and only the adjustment knob is visible on the surface. In such cases, the unit itself is hidden behind a plastic panel or directly in thermal insulation behind the rear wall of the chamber.
In more modern two-chamber models, the mechanical thermostat is often hidden in the upper part of the refrigerator compartment, above the door or in the lampshade. Sometimes to access it you need to remove the top cover of the refrigerator or a decorative panel. If you have a refrigerator No Frostthen the mechanical thermostat (if there is one, and not electronics) is usually hidden in the technical compartment at the back, near the compressor, or behind the rear panel inside the chamber.
Electronic sensors are always located in the area whose temperature they are supposed to measure. Look for them:
- 🔍 On the back wall inside the chamber (often in a plastic casing).
- 💡 Next to the lighting lamp (in older models, the lamp affected the readings).
- 🌪️ In the cold air outlet area (for the No Frost system).
⚠️ Attention: The design of refrigerators of different brands can differ significantly. The location of the components depends on the specific series and year of manufacture. If you cannot find the part according to the description, check the technical documentation or diagrams for your specific model on the manufacturer's official website.
Why is the thermostat hidden?
Engineers try to remove the thermostat away from the heat source (lamp) and drafts so that the readings are as accurate as possible. In older models this was not always possible, so the handle was often hidden deep in a niche so that the user would not accidentally change the settings.
Table: Comparison of mechanical and electronic thermostats
To finally understand what type of device you are dealing with, it is convenient to compare their key characteristics. This will help not only in diagnostics, but also when searching for a spare part in online stores.
| Characteristics | Mechanical thermostat | Electronic sensor (thermistor) |
|---|---|---|
| Appearance | Box with a tube and handle | Small probe on the wire |
| Principle of operation | Gas expansion in the bellows | Change in electrical resistance |
| Accuracy | Error 2-4 degrees | High accuracy (up to 0.5 degrees) |
| Checking | Ringing contacts with a tester | Resistance measurement at different temperatures |
As can be seen from the table, a mechanical thermostat is a universal devicewhich physically opens the circuit, while the electronic sensor only transmits data to the control board, which already makes the decision to start the compressor. This fundamental difference also determines the difficulty of repair: mechanics can often be replaced with an analogue, but electronics must be looked for strictly by article number.
Visual signs of a malfunctioning thermostat
Understanding what a working device looks like helps identify defects. During an external inspection of a mechanical thermostat, the integrity of the capillary tube is first checked. If the copper tube has dents, creases, or, worst of all, traces of oil (freon leakage from the sensor), then the device is faulty. Also, a sign of a problem may be a melted plastic case, which indicates overheating of the contacts or poor connection of the wires.
For electronic sensors, visual diagnostics are more difficult. Often a wire break occurs inside the insulation, closer to the entrance to the sensor housing or at the junction with the cable. Carefully inspect the wire along its entire length for microcracks, traces of rodents or melting. Oxidation of the contacts on the connector can also cause a failure in the transmission of temperature data.
Indirect signs indicating problems with the thermostat are:
- 🧊 Constantly running compressor (the refrigerator does not turn off).
- 🔥 The compressor is silent; the chamber is warm (no start).
- 💧 Excessive formation of ice or, conversely, complete defrosting of food.
☑️ Diagnostics of the thermostat
Nuances of markings and article numbers
If you get to the visual inspection of the part and If you plan to buy one, you will have to face the world of factory markings. There is always a stamp on the body of a mechanical thermostat with an alphanumeric code (for example TAM 133, K 59, RANCO K50). These letters and numbers determine the length of the tube, the operating temperature range and the type of fastening.
Two thermostats may look exactly the same, have the same tube length and the same handle, but different on and off temperatures. Installing the wrong model will result in the refrigerator either not freezing or overfreezing food. Therefore, when searching for an analogue, you need to focus not only on appearance, but also on technical parameters.
For electronic sensors, markings are often applied to the connector itself or to the wire tag. Here, not only the shape of the probe is important, but also the nominal resistance at a certain temperature (for example, 10 kOhm at 25°C). Different manufacturers use different standards, so a “similar” sensor from another brand may not work correctly.
Frequently asked questions (FAQ)
Is it possible to temporarily short-circuit the thermostat wires to make the refrigerator work?
Yes, a mechanical thermostat can be temporarily excluded from the circuit by connecting the wires directly. This will make the compressor run continuously. However, this is an emergency measure: without temperature control, the refrigerator will turn into a freezer, food will freeze, and the compressor may burn out from overload. Use this method only for short-term defrosting or evacuating food.
Why is the tube longer on the new thermostat than on the old one?
The capillary tube is often made with extra length for versatility. The excess tube can be carefully wound into a ring (at least 5 cm in diameter) and secured with a clamp inside the refrigerator body, but not in the freezer. The main thing is not to cut the tube or create sharp kinks.
How to understand that it is the thermostat that has failed, and not the compressor?
If, when the thermostat wires are shorted (bypassing it), the compressor starts and starts to cool, then the problem is in the regulator. If, even with a direct connection, the compressor is silent or hums, but does not start, the problem is in the start relay, the compressor itself, or the lack of refrigerant.
Is it possible to repair a mechanical thermostat?
In the factory, these devices are not repairable, since the housing is sealed or filled with compound, and calibration produced on special equipment. In everyday life, an attempt to disassemble and adjust the screws under the seal, as a rule, leads to final failure. It’s easier and more reliable to buy a new one.