The thermal relay (or thermostat) is the “brain” of the refrigerator, which controls the temperature in the chambers and controls the operation of the compressor. When this unit fails, the equipment begins to behave unpredictably: it either freezes without stopping, or refuses to turn on at all. In 70% of cases, a thermostat malfunction can be diagnosed independently, without resorting to the services of a service center.
But how to distinguish a thermostat failure from problems with the compressor or freon leak? In this article we will examine thermal relay checks at home - from visual inspection to testing with a multimeter. You will learn what tools you will need, how to take readings correctly, and what to look for when replacing a part. And also typical mistakes that beginners make when making repairs. 5 proven methods checking thermal relays at home - from visual inspection to testing with a multimeter. You will learn what tools you will need, how to take readings correctly, and what to look for when replacing a part. And also typical mistakes that beginners make when repairing.
⚠️ Important: If your refrigerator is still under warranty, self-diagnosis can lead to its cancellation. Check the conditions in the warranty card before starting work.
Signs of a faulty thermostat: when is it time to check
The first signal of problems with the thermostat is inappropriate behavior of the refrigerator. But the same symptoms may indicate other problems. In order not to waste time, pay attention to the following “bells”:
- 🔴 The compressor runs without stopping - the motor hums constantly, without turning off for rest. Normally, the “work/rest” cycle should be repeated every 20-30 minutes.
- ❄️ Formation of “snow” fur coats" on the back wall of the refrigerator compartment (in models with a drip system) or excessive icing of the freezer.
- 🌡️ The temperature in the chambers does not correspond to the settings —the food freezes or, conversely, deteriorates from the heat.
- 🔌 The refrigerator does not turn on completely —there is no sound of the motor running, the indicators do not light up (provided that the socket is working).
- 🔄 Spontaneous shutdown —the equipment suddenly turns off and does not respond to a restart.
If at least one of these signs appears, the probability of a thermal relay failure is 50-80% (according to statistics from repair services). However, before checking, rule out other reasons:
- 🔌 Power supply problems - check the socket, plug and power cord.
- 🧊 Clogged drainage - in models No Frost this may simulate a thermostat malfunction.
- 🛠️ Door not closed tightly —even a small gap disrupts the temperature regime.
Where is the thermostat located and how to get it
The location of the thermostat depends from refrigerator model and type. In most cases, it can be found in the following places:
| Refrigerator type | Thermal relay location | Access features |
|---|---|---|
| Modern No Frost (Samsung, LG, Bosch) | For plastic panel inside the refrigerator compartment (next to the lamp) | You need to remove the protective cover by snapping the latches |
| Old Soviet (ZIL, Minsk, Atlant) | Outside, on the right wall (under the plastic lid) | Attached with 2-3 screws, the sensor tube goes inside the chamber |
| Two-chamber with bottom freezer (Indesit, Ariston) | In the upper part of the refrigerator compartment, under the lid | Often combined with a regulator temperature |
| Built-in models | On the rear wall (access from the compressor side) | You will need to move the refrigerator away from the wall |
To remove the thermal relay, follow the algorithm:
- Disconnect the refrigerator from the mains and defrost it (if there is ice).
- Remove the protective panel or cover (can be secured with latches or screws).
- Disconnect the wire terminals from the thermostat - take a photo of their locationto avoid confusion when returning assembly.
- Carefully remove the capillary tube (temperature sensor) from the housing.
☑️ Preparing to check the thermal relay
⚠️ Attention: c refrigerators with electronic control (for example Samsung RB37J5240SA or LG GB-B459SLQZ), the thermal relay may be part of the control board. In this case, diagnostics require special equipment, and it is better to contact the service.
Method 1: Checking the thermal relay without instruments (visual inspection)
If you don’t have a multimeter at hand, start with external inspection. This method does not provide a 100% guarantee, but it helps to identify obvious defects:
- 🔍 Oxidation of contacts - green or white coating on the terminals indicates poor contact. Clean them with alcohol and fine sandpaper.
- 💧 Traces of corrosion on metal parts - rust can disrupt the operation of the mechanism.
- 🧲 Deformation of the capillary tube - if it is pinched or torn, the thermostat will not read correctly temperature.
- 🔧 Damage to the plastic case —cracks or chips may indicate mechanical damage.
Also try scroll the temperature regulator (if it is mechanical B). In a working thermostat, you should hear a slight click when switching modes. If the regulator rotates too easily or, conversely, jams, this is a sign of a malfunction.
For more accurate diagnostics, you can use freeze test:
- Remove the thermostat from the refrigerator without disconnecting the capillary tube.
- Place the sensor (metal tip of the tube) in a container with ice for 10-15 minutes.
- If the thermostat is working properly, a click should be heard after 1-2 minutes - this is the contact group.
If there is no click, the thermostat is faulty. If there is a click, but the refrigerator still does not work, the problem may lie in the compressor or start relay.
Method 2: Checking with a multimeter (step-by-step instructions)
For accurate diagnostics you will need digital multimeter (even a budget model like DT-830Bis suitable; the thermal relay is checked in two modes: on open circuit and). on contact resistance.
Preparation:
- Disconnect the thermal relay from the refrigerator, leaving only the wires connected to the refrigerator itself thermostat.
- Set the multimeter to mode
continuity(diode or sound wave icon).
Test procedure:
- Open circuit test:
- Connect the multimeter probes to the contacts
3 and 4(usually they are marked). - If on the display
1orOLthe circuit is open, the thermal relay is faulty. - If a signal sounds or is shown the resistance is close to
0—there is contact, proceed to the next step.
- Connect the multimeter probes to the contacts
- Place the thermostat sensor in hot water (+50°C) for 1-2 minutes.
- Ring contacts
3 and 4again - when heated, the circuit should open (readings1orOL). - Cool the sensor with ice - the circuit should closed (signal or
0). - Connect the battery to the contacts
3 (+) and 4 (-)thermal relay through a 1.5 V light bulb (can be taken from a flashlight). - Place the sensor in hot water - if the thermostat is working, the light bulb will go out (the circuit will open).
- Cool the sensor with ice - the light bulb should light up (circuit will close).
- Disconnect the tube from the thermostat (carefully so as not to bend it!).
- Blow into the tube. - if it is tight, air should not pass through.
- Immerse the end of the tube in hot water - if the gas inside has evaporated, the tube will shrink easily.
⚠️ Attention: in some thermal relay models (for example, Danfoss 077B6 or Ranco K59) the contacts may be marked differently. Check the diagram, which is usually printed on the body of the part.
How to check a thermal relay with 6 contacts?
In six-pin thermostats (for example, in refrigerators Stinol), pairs of contacts are responsible for different modes. To check, ring pairs 1-2, 3-4 and 5-6. In operating condition, 1-2 and 3-4 should close when cooling, and open when heating.
| Multimeter readings | Thermal relay status | Actions |
|---|---|---|
| The circuit is open in both states | The contact mechanism is faulty | Replacing the thermal relay |
| The circuit is closed in both states | Contacts are stuck | Try to clean the contacts or replace |
| The circuit closes/opens when the temperature changes | The thermal relay is working properly | Look for the cause in other nodes |
Method 3: Testing with a battery (express test)
If you don’t have a multimeter and the thermal relay is mechanical, you can use a 1.5-9 battery. In (for example, “Krona”). This method is suitable for models with a simple contact group.
Instructions:
If the light bulb does not respond to temperature changes, the thermostat is faulty. Please note: this method does not work for electronic thermostats and models with control boards.
Method 4: Diagnostics by capillary tube resistance
Thermal relay capillary tube is full with freon or special gas, which reacts to temperature. If the tube is damaged, the thermostat will not work correctly. You can check its integrity as follows:
⚠️ Attention: do not try to straighten or solder the capillary tube! is filled with refrigerant under pressure, and if damaged, gas will escape, making the thermostat inoperative.
If the tube is damaged, you will have to replace the entire thermostat - capillary sensors are not sold separately The cost of a new thermostat for popular models:
- 💰 Atlant, Minsk, ZIL —. 800–1500 rubles
- 💰 Indesit, Ariston, Beko — 1200–2500 rubles.
- 💰 Samsung, LG, Bosch —2000–4500 rubles (depending on the model).
- Disconnect the refrigerator from the network.
- Remove the old thermostat without disconnecting the capillary tube (if it is working).
- Connect known working thermostat the same model, observing polarity.
- Turn on the refrigerator and check if the compressor is working.
- 🔌 Refrigerant type (R134a, R600a, etc.).
- 📏 Length of the capillary tube (must correspond to the original).
- 🔧 Number of contacts (3, 4 or 6).
- 🔌 Ring the thermal relay without disconnecting it from the refrigerator this can damage the control board.
- ❄️ Use too hot water for the test (above +60°C) — this deforms the capillary tube.
- 🔧 Mix up the contacts when connecting —this leads to a short circuit.
- 📏 Ignore the markings —thermal relay from Indesit is not suitable for Samsung, even if it looks similar.
- 💡 Check electronic thermostats without a circuit —they require special tests.
- 🔧 Oxidized contacts —they can be cleaned with sandpaper and treated with alcohol.
- 🔩 Loose terminals —tighten with a screwdriver.
- 🧲 Pressed capillary tube — carefully straighten (if there are no breaks).
- Buy analogue of the original part (marking is indicated on the body of the old one relay).
- Move the capillary tube from the old thermostat (if it is working).
- Connect the wires, observing the polarity (use the photo taken before removal).
- Install the thermostat in place and check the operation of the refrigerator.
- 🔌 Tightness of contacts - a weak connection will lead to heating and reflow.
- 🧊 Integrity of the capillary tube —do not bend it.
- 🔧 Tightness housing —after installation there should be no gaps.
- Disconnect the refrigerator from the power supply.
- Remove the protective cover of the thermal relay (if it exists).
- Find the two wires going to the contacts
3 and 4and test them with a multimeter. - Change the temperature with the regulator - when activated, there should be a click and a change in resistance.
- Does not start at all (no humming).
- It hums, but does not pump up the cold (you can hear the clicking of the start relay).
- Strongly heats up (the compressor housing is hot).
- The compressor runs without stopping or does not turn on.
- The temperature in the chambers does not correspond to the settings.
- The relay clicks are heard, but the motor does not respond.
- Phillips and flathead screwdrivers.
- Multimeter (for checking the new thermal relay).
- Pliers (for crimping terminals).
- Insulating tape or heat shrink tube (for insulating connections).
- You have already removed the thermal relay to check.
- There is access to the back wall of the refrigerator.
- The new relay fits the model.
- Work without stopping, which will lead to overheating and breakdown.
- Refreeze food (the temperature will drop to -20°C and below).
- Consume 2-3 times more electricity.
Method 5: Checking with by replacing it with a known-good relay
If you are not sure of the test results, the most reliable way is connect a working thermostat from another refrigerator (for example, take it from a neighbor or from a service center for testing. This method eliminates diagnostic errors.
How to carry out). test:
If the refrigerator works fine with the new thermostat, the problem is in the old relay. If not, look for a fault in the compressor, start relay or control board.
⚠️ Attention: not all thermostats. interchangeable! Make sure that the model is suitable for:
Typical errors when checking a thermal relay
Even experienced craftsmen sometimes make mistakes that lead to incorrect diagnosis. Here's what you can't do when checking:
Also Many people forget that The thermostat may be working properly, but incorrectly calibrated.. For example, if the temperature regulator is set to maximum, the compressor will work without stopping, simulating a breakdown. Before diagnosing, make sure that the thermostat knob is in the middle position.
What to do if the thermostat is faulty: repair or replacement
In most cases The thermostat cannot be repaired - it is replaced with a new one:
If the thermal relay needs to be replaced:
The cost of replacement in the service will cost 1500–3500 rubles. (depending on the model). If you decide to do this yourself, keep an eye on:
After replacing, let the refrigerator operate for 2-3 hours in normal mode, then check the temperature in the chambers with a thermometer.
FAQ: Frequently asked questions about checking the thermal relay
Is it possible to check the thermal relay without removing it from the refrigerator?
Yes, but only in models with mechanical control. To do this:
However, such a test is less accurate, since it does not take into account the condition of the capillary tube.
How to distinguish a malfunction of the thermostat from a breakdown of the compressor?
If there is a problem in compressor, it:
If the problem is in thermal relay:
What tools are needed to replace the thermal relay?
Minimum set:
For some models (Samsung, LG) you may need an 8 or 10 socket wrench mm.
How long does it take to replace a thermal relay?
On average - 30-60 minutesif:
In difficult cases (for example, if you need to solder contacts or change a capillary tube), the work can take up to 2-3 hours.
Is it possible to use the refrigerator without thermal relay?
Technically yes, but highly not recommended. Without a thermostat, the compressor will:
If the thermostat is broken and a new one is not at hand, you can temporarily connect the compressor via a time relay (for example, for 20 minutes of operation/40 minutes of rest), but no more than 1-2 days.