The situation when the refrigerator stops turning off or, conversely, stops freezing, always takes you by surprise. In most cases, the cause of temperature failures is thermostat, which is responsible for turning the compressor on and off. Diagnostics of this unit is a key step before deciding to call a technician or repair it yourself.
Understanding the principle of operation thermostat allows you to avoid unnecessary expenses for diagnostics from specialists. If the device fails, the compressor can work without interruption, “winding up” kilowatts, or remain silent for days, leading to food spoilage. In this article we will look at how to identify a malfunction without complex equipment.
Before starting any manipulations with electrical components, it is necessary to completely de-energize the unit. Unplug the socket and gain access to the rear wall or interior panel where the regulator is located. Ignoring safety rules when working with electrical appliances is unacceptable.
⚠️ Attention: Any work on diagnosing the internal circuits of the refrigerator is carried out only after complete disconnection from the power supply. Residual charge in capacitors can be dangerous.
Main signs of a malfunctioning thermostat
The first signal of problems with thermostat is a change in the usual operating mode of the compressor. If the motor hums without stopping and does not turn off even when a “coat” of ice has formed inside the chamber, this is a clear symptom of sticking contacts or loss of sensitivity of the sensor. In such a situation, food can freeze, and excess ice appears on the walls.
The opposite situation is also typical for a breakdown: the refrigerator is silent, the light inside is on, but there is no cold. The compressor does not start because thermostat it does not close the circuit, “thinking” that the temperature is normal. This often happens when the bellows tube breaks or the contact group oxidizes. In some cases, the unit may turn on for a couple of seconds and immediately click, going into protection.
It is worth considering that symptoms may vary depending on the design of your model. To accurately assess the situation, it is useful to know what kind of deviations are observed.
- 🔊 The compressor works continuously, without turning off for hours.
- ❄️ The temperature in the chamber is significantly lower or higher than the set one.
- ⚡ The unit does not turn on at all, although there is voltage in the network.
- 💧 The appearance of a large amount of water or ice build-up.
Visual inspection and initial check
Before grabbing the multimeter, conduct a thorough visual inspection accessible elements. Often the reason lies in mechanical damage to the capillary tube or oxidation of the contacts. Remove the regulator knob and plastic trim to access the device body. Inspect the wires for melting or breakage.
Pay attention to the bellows tube (capillary) that runs inside the chamber. If it shows signs of corrosion, dents, or is disconnected from the evaporator, the tightness of the system is broken. Inside the tube is a gas or liquid that reacts to changes in temperature. If damaged, freon evaporates, and the thermostat stops feeling cold.
Also check the condition of the contacts. If they are blackened or coated with carbon deposits, this can cause sparking and unstable operation. In some models, you can try to “revive” the regulator by cleaning the contacts, but this is a temporary measure.
Is it possible to restore the tightness of the tube?
It is almost impossible to solder the thermostat capillary tube yourself at home. Special equipment is required for gas filling and calibration. It is easier and more reliable to replace the entire assembly.
For example, in models Indesit or Ariston access to the thermostat is often located inside the chamber, and in LG or Samsung on the rear panel.
⚠️ Attention: Do not try to straighten a deformed capillary tube by force. Thin metal will easily burst, which will completely damage the part.
Removing the thermostat for diagnostics
To carry out an accurate check, the device will have to be removed. The dismantling process depends on the location thermostat. If it is inside the camera, carefully remove the plastic casing, unscrew the mounting screws and remove the device by pulling it towards you. The capillary tube will come out of the hole in the wall.
If the regulator is located outside, on the back wall of the refrigerator, remove the protective cover. Disconnect the wires after first remembering or photographing the connection diagram. Wire colors may vary, but they are usually labeled or have a standard color code. Disconnect the tube from the evaporator if it is secured with a clamp.
Be careful when removing the long bellows tube so as not to damage it and adjacent elements of the cooling system. After removal, you will have in your hands a device with several terminals for connecting wires.
☑️ Dismantling procedure
Diagnostics with a multimeter: step-by-step instructions
The most reliable way how to check the refrigerator thermostat is to use a multimeter in dial mode. This device will show whether the electrical circuit is closed when the temperature of the sensing element changes. Switch the tester to resistance measurement mode (Ohm) or audio continuity.
Connect the multimeter probes to the contacts of the thermostat. Usually there are two or three. If you have three pins, the third is often used to connect an indicator light or ground, you can ignore it for now, calling the main working pins. At room temperature, the contacts should be closed (the device beeps or shows zero).
Now the most important step is checking the reaction to cold. Immerse the sensing tube in a container of water mixed with ice for a few minutes. Or just cool it very much (you can press it with an ice pack). If thermostat is working, when a certain temperature is reached (usually about -5..-10°C) a click should be heard and the circuit will open (the multimeter will go silent or show one/infinity).
| Contact state | At room temperature | When the tube is cooled | Diagnosis |
|---|---|---|---|
| Closed | Yes (0 Ohm) | Open (∞) | Good |
| Closed | Yes (0 Ohm) | Closed (0 Ohm) | Faulty (not opens) |
| Open | No (∞) | Open (∞) | Faulty (break) |
| Unstable | Jumping | Jumping | Burning of contacts |
If there is no click when cooling and the resistance does not change, it means thermostat faulty and requires replacement. Lack of response indicates loss of tightness of the bellows or mechanical jamming of the mechanism.
Alternative methods of checking without multimeter
What to do if you don’t have a tester at hand? There is a less accurate but workable "straight jumper" method. It allows you to understand whether the compressor is alive and the problem is in the regulator. To do this, you need to short-circuit the wires going from the network to the thermostat, bypassing the device itself.
Remove the wires from the contacts of the thermostat and connect them directly to each other (using insulated wiring or twisting). Plug in the refrigerator. If the motor-compressor starts and hums, it means that everything is in order with the engine and the starting relay, and thermostat really does not close the circuit. If the compressor is silent, the problem is deeper (relay, motor or wiring).
This method is good for quick diagnosis, but you cannot leave the refrigerator in this state for a long time. Without temperature control, it will freeze until it stops until you manually unplug it. This can lead to defrosting of the evaporator during subsequent shutdown or damage to the products.
- ⚡ The jumper method confirms the operability of the compressor.
- 🚫 It is strictly forbidden to leave the jumper for a long time.
- 🔥 Risk of motor overheating during operation without shutdown is very high.
⚠️ Attention: When using the jumper method, strictly monitor the temperature in the chamber. Do not leave the refrigerator turned on unattended for more than 15-20 minutes to avoid defrosting or overheating.
Replacement and selection of a new thermostat
If diagnostics confirm a breakdown, thermostat needs to be replaced. It is impractical to repair it: factory calibration requires special equipment. 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.
Markings are usually applied to the body of the device. Pay attention to the number of contacts and their location. When installing a new tube, try not to damage it and place it correctly in its normal place on the evaporator, securing it with a standard clamp. Poor contact of the tube with the evaporator wall will lead to incorrect operation of the refrigerator.
After assembly, turn on the unit and check its operation for several hours. The compressor must periodically turn on and off, maintaining the set temperature.
Is it possible to use a thermostat from another refrigerator?
Using an analogue is possible only if the temperature range, capillary tube length and type of fastening match. Different models may have different sensitivity, which will lead to the compressor not working properly.
Why does the refrigerator click but does not turn on?
Clicks can come from the thermostat contacts or the start relay. If the thermostat is working properly (it rings), but there are clicks, there is probably a problem in the compressor start relay or the motor itself.
How often do you need to change the thermostat?
The service life of the thermostat is usually 5-10 years or more. Scheduled replacement is not required, only when signs of malfunction appear.
Does defrosting affect the operation of the thermostat?
Proper defrosting does not affect. However, using sharp objects to chip ice can lead to breaking the thermostat capillary tube if it runs near the evaporator.