A sudden stop of the compressor or, conversely, its endless operation often indicates a failure of the thermostat. This small device is responsible for maintaining a given temperature inside the chambers, closing and opening the electrical circuit depending on the sensor readings. If you notice that food has begun to deteriorate or the ice coat has frozen, the first thing you should think about is diagnosing this particular element. Temperature relay (or thermostat) is the heart of the cooling control system, and its breakdown completely paralyzes the operation of the unit.
Independent testing allows you to save a significant amount on the call masters, since the procedure does not require complex equipment. You will only need a basic set of tools and minimal knowledge of electrical engineering. In this article, we will analyze in detail the algorithm of actions that will help determine whether the problem lies in the thermostat or the malfunction is of a deeper nature. It is important to understandthat timely diagnosis prevents food spoilage and more expensive compressor repairs.
The main signs of a malfunction of the thermostat
Before you start disassembling the refrigeration equipment, you need to make sure that the diagnosis is correct. Symptoms of breakdown thermostat are often obvious, but they can be confused with other problems. For example, if the compressor does not turn on at all, but the light inside is on, this may indicate either an open circuit in the relay or problems with the starting device or the motor itself. However, if the engine hums but does not start, or runs nonstop, most likely the temperature sensor is to blame.
Pay attention to the nature of the unit’s operation. A working refrigerator should cycle on and off. If you observe one of the following scenarios, the probability of relay failure is extremely high. When the relay contacts stick, the compressor runs continuously, causing severe freezing of the evaporator even at minimum settings.
⚠️ Attention: If the compressor runs continuously for more than 24 hours, this creates a critical load on the engine's service life. Do not delay diagnostics to avoid costly compressor replacement.
There are a number of indirect signs that may also indicate a problem with the thermostat. They do not always appear in combination, but their presence should alert the owner of the equipment.
- 🧊 The appearance of a “snow coat” or ice on the back wall of the refrigerator compartment, even if the operating mode has not changed.
- 🔊 Characteristic clicks when trying to start the compressor, after which the motor is silent or immediately stalls.
- 🌡️ Defrosting food in the main chamber with the compressor running but not turning on periodically.
- 💧 The appearance of puddles under the refrigerator due to the melting of ice, which does not have time to evaporate.
Where is the thermostat and how to get to it
Location thermostat depends on the model and year of manufacture of the refrigerator. In older models, such as Atlant or Biryusa Soviet period, the regulator is often located inside the refrigerator compartment. The control handle is usually located on the inside wall or at the top of the chamber, and the relay housing itself is hidden behind a plastic panel. To get to it, you need to remove the regulator handle and unscrew the fastening screws.
In modern models, including equipment Indesit, LG i Samsung, the design may be more complex. Often the thermostat is hidden in a niche above the door or in a special compartment in the upper part of the case. In some cases, access requires partial disassembly of the internal space. Capillary tube, which is a sensitive element, is built into the evaporator or mounted on the rear wall of the chamber.
The dismantling process requires care so as not to damage the fragile plastic latches and the capillary tube itself. Proceed according to the following algorithm:
- De-energize the refrigerator by unplugging the power cord from the outlet.
- Remove the decorative trims and temperature control knob.
- Carefully remove the thermostat housing, paying attention to the length of the capillary.
- Disconnect the electrical wires by first photographing their location.
Features of the capillary tube
The capillary tube is filled with freon or other gas-sensitive substance. When heated, the gas expands and opens the contacts; when cooled, it contracts, closing the circuit. Do not bend or squeeze the tube under any circumstances, as a leak in the seal will make the device beyond repair.
Visual inspection and initial diagnostics
After removing the relay from its seat, conduct a thorough visual inspection. Often external signs can suggest the cause of a malfunction without the use of measuring instruments. Inspect the housing for cracks, melts, or traces of soot. If you see blackened contacts or a burning smell, this is a sure sign that a short circuit or overload has occurred inside.
Pay special attention to the condition capillary tube. It should be smooth, without creases or swelling. If traces of corrosion or mechanical damage are visible on the tube, the tightness of the system is broken and the gas has escaped. In this case, the relay will not be able to respond correctly to temperature changes, and its replacement is inevitable.
Check the reliability of the wires in the terminals. Oxidized or loose contacts can give the false impression that the relay itself is faulty. If visually the device looks intact, proceed to an instrumental check. Multimeter will become your main assistant at this stage.
Checking the temperature relay with a multimeter
The most accurate diagnostic method is to use an electronic measuring device. Multimeter allows you to check the integrity of the circuit and the operation of the contacts in different temperature conditions. To carry out the test, switch the device to continuity mode (usually indicated by a speaker symbol) or resistance measurement (Ohm).
First, test at room temperature. Touch the multimeter probes to the relay contacts. If the thermostat is working properly and is designed to open when the temperature rises, then at room temperature (about +20°C) the contacts should be closed. The device should beep or show a resistance value close to zero. The absence of a signal indicates a break inside the device.
Next, you need to check the relay’s response to cold. To do this, place the sensitive part of the thermostat (capillary tube with a cone) in a container with cold water and ice for 15-20 minutes. The temperature should drop to approximately 0...-5°C. After cooling, repeat the contact test. Depending on the type of relay, the circuit should break (infinity resistance) or remain closed, but change its characteristics.
☑️ Algorithm for checking with a multimeter
Measurement results can be interpreted using the following table:
| Contact state | Environment temperature | Multimeter readings | Verdict |
|---|---|---|---|
| Closed | Room (+20°C) | 0 Ohm (Sound is present) | Normal |
| Open | Room (+20°C) | ∞ (No sound) | Faulty (break) |
| Closed | Cooling (0°C) | 0 Ohm (Sound present) | Stuck/Faulty |
| Open | Cooling (0°C) | ∞ (No sound) | Normal (for most) |
⚠️ Attention: Some thermostat models have normally open contacts. Before diagnosing, study the markings on the case or the technical documentation of a specific model so as not to make false conclusions.
Elimination method: testing without instruments
What to do if you don’t have a multimeter at hand? There is a popular method of verification, which is often called the “method of exclusion” or “closure”. It is based on a direct connection of the compressor, bypassing the thermostat. This method allows you to understand whether the refrigerator motor and the start relay are alive, but requires increased caution.
To implement the method, it is necessary to connect the wires coming from the thermostat directly to each other, excluding the device itself from the circuit. It is important not to mix up the wires and avoid contact with the metal case. If, after connecting to the network, the compressor started working and began to freeze, then the problem lies precisely in the thermostat.
However, this method has a significant drawback: the refrigerator will work continuously until you turn it off manually. Hypothermia products and failure of the compressor due to overheating are guaranteed if you leave the system in this mode for a long time. Use this method only for short-term diagnostics (for 5-10 minutes).
- ⚡ Disconnect the wires from the thermostat terminals.
- 🔗 Connect them together using insulating tape or twisting.
- 🔌 Plug in the refrigerator.
- 👂 Listen to the compressor start: if it works, the thermostat is faulty.
Replacing the thermostat: step-by-step instructions
If diagnostics confirm a malfunction, the only solution is to replace the element. Repairing the insides of the thermostat at home is neither possible nor practical. The new device must fully comply with the characteristics of the old one: the length of the capillary tube, the temperature range and the type of contacts.
The marking is usually applied to the body or to the regulator handle. Look for codes like TAM-133, K-59, K-50 or RANCO. When purchasing, pay attention to the length of the capillary - if it is too long, the tube will have to be carefully placed in specially designated channels to avoid damage. A short capillary may not reach the control zone, which will lead to incorrect operation.
The installation process is as follows:
- Install the new thermostat into the seat, carefully straightening the capillary tube.
- Fix the housing with screws and install decorative linings.
- Connect the wires according to the diagram or photograph made earlier.
- Turn on the refrigerator and check its operation in different modes.
⚠️ Attention: Do not bend the capillary tube at an acute angle and do not allow it to touch moving parts or hot elements. This can lead to depressurization and instant failure of the new relay.
Where to buy an original thermostat?
It is better to look for original spare parts by the refrigerator model code in specialized stores or service centers of the brand. Analogs may work less stably and have a shorter service life.
After replacement, it is recommended to carry out a control cycle of operation. Set the average temperature value and record the operating and resting time of the compressor. Normally, the refrigerator should get cold, turn off and stand for some time. If it is a cycle, it means you have successfully completed the task.
Frequently asked questions (FAQ)
Is it possible to repair the thermostat yourself?
Theoretically, you can try to clean the burnt contacts if the case is collapsible, but this is a temporary measure. The tightness of the gas chamber is broken when opened, so it is safer and more reliable to completely replace the unit.
Why doesn’t the new thermostat click?
Some modern electronic relays operate silently. If we are talking about a mechanical device, the absence of a click when the temperature changes may indicate a defect or incorrect installation of the sensitive tube.
How often do you need to change the temperature switch?
The service life of the thermostat is usually 5-10 years, depending on the intensity of use and the quality of the electrical network. There is no specific replacement schedule; they are replaced only when malfunctions occur.
Does defrosting affect the operation of the relay?
Regular defrosting prolongs the life of the entire system, including the thermostat. Working in conditions of heavy ice forces the relay to operate in extreme modes, which can shorten its life.
What to do if the capillary tube is longer than the old one?
Excess tube cannot be cut off. It must be carefully rolled into a ring (with a diameter of at least 3-4 cm) and placed in a free space inside the case or behind the back wall, avoiding kinks.