Brand refrigerators Posis are deservedly considered one of the most reliable units on the domestic market, however, even such proven equipment can fail over time. One of the most common reasons why a compressor stops starting or operates intermittently is the failure of the starting or thermal relay. This small device is responsible for supplying voltage to the motor windings, and its breakdown completely stops the cooling process of the chambers.
Before calling a technician or buying a new compressor, it is necessary to conduct a thorough diagnosis of this particular element. In most cases, the problem lies in a burnt winding or stuck contacts, which is easily fixed by replacing the part. Understanding how to properly check the relay in a refrigerator Posiswill save you significant money and time, returning the equipment to working order.
In this article we will analyze in detail the design of the starting system, symptoms of malfunctions and a step-by-step testing algorithm using a multimeter. You will learn how to distinguish a relay breakdown from more serious problems with the motor and what to look for when visually inspecting the contacts.
The operating principle and types of relays in Pozis refrigerators
The compressor starting system in refrigerators Position is based on the use of a starting and thermal relay, which are often combined into a single one structural block. The starting relay is necessary for short-term connection of the starting winding of the engine at the moment of switching on, creating torque. The thermal relay, in turn, performs a protective function by breaking the circuit in case of overheating or overcurrent, preventing combustion of the compressor windings.
In modern and older models, different types of devices can be used. The most common are electromagnetic starting relays, where the contacts close under the influence of current passing through the solenoid. There are also posistor (solid-state) relays that do not have moving mechanical parts and work by changing the resistance of the semiconductor element when heated.
It is important to understand that starting relay and a thermal relay are two different functional elements, even if they are physically located in the same case. A malfunction of one of them leads to the fact that the compressor either hums but does not start, or turns on and immediately turns off. For accurate diagnostics, you need to know the type of device installed in your model.
- 🔌 Electromagnetic relays: have a movable core and contacts, are subject to mechanical wear and sticking.
- 🔥 PTC relays: have no moving parts, fail less often, but they require time to cool down before restarting.
- 🛡️ Thermal relay: contains a bimetallic plate that bends when heated and opens the power circuit.
You can determine the type of relay by its appearance and markings. If a coil and a moving mechanism are visible inside the housing, it is an electromagnetic type. If the device is a sealed plastic cube with three contacts, it is most likely a posistor. In refrigerators Posis there are often combined units where the thermal protection is built directly into the body of the starting device.
Symptoms of a faulty starting device
Diagnostics of any household appliance should begin with an analysis of the symptoms. If your refrigerator Pozis stops freezing, but still makes characteristic sounds, the problem most likely lies in the starting system. Ignoring these signs can lead to more expensive repairs, including replacing the compressor itself.
One of the most obvious signs is when the compressor tries to start, there is a loud click, the hum lasts a few seconds, and then another click and silence. This means that thermal relay triggered because the engine is unable to spin up and breaks the circuit to prevent overheating. After some time, the cycle repeats.
You should also pay attention to the following signs:
- 🔊 A loud metallic click when you turn on the refrigerator.
- 🌡️ The compressor heats up to a very high temperature, but does not works.
- 💡 Flashing light in the room when trying to start the unit.
- ❄️ Lack of cold in the chambers when the lighting is on.
⚠️ Attention: If the compressor hums for more than 10-15 seconds and does not start, immediately unplug the refrigerator. Long-term operation in this mode (“jammed”) is guaranteed to lead to an interturn short circuit of the motor windings.
Sometimes a situation occurs when the relay simply does not make any sounds and the compressor is silent. This may indicate an open circuit in the relay itself or a lack of voltage due to problems with the thermostat or wiring. In any case, a visual inspection and a “test” with a multimeter will give an accurate answer.
It is important to note that the symptoms may be similar if the compressor itself is faulty (for example, a piston group wedge). Therefore, checking the relay is the first and mandatory step to eliminate problems that are simple and cheap to fix.
Preparation for diagnostics and safety precautions
Before you start checking the refrigerator relay Posisit is necessary to ensure safe working conditions. Electrical current combined with moisture and metal tools creates a risk of injury. In addition, careless actions can damage the integrity of copper tubes or electrical contacts.
The first step should always be to completely disconnect the unit from the power supply. It is not enough to simply turn off the button, if there is one - you need to unplug the plug from the socket. Only after this can you begin to dismantle the rear panel and gain access to the compressor.
To carry out high-quality diagnostics you will need the following tools:
- 🔧 Screwdrivers (Phillips and flat) for removing the casing and terminals.
- 🔌 Multimeter (tester) for measuring resistance and checking integrity circuits.
- 🧤 Dielectric gloves to protect hands (optional, but recommended).
- 🧼 Sandpaper or needle file for cleaning contacts.
If you find that there are traces of melting, burning or a characteristic smell of burnt plastic on the relay or wires, this is a sure sign that the part requires replacement. However, even if the device visually looks intact, the internal winding could have burned out, so checking with a device is mandatory.
During operation, try not to sharply pull the wires suitable for the compressor, as they can be fragile from time and temperature. Carry out all manipulations carefully so as not to damage the insulation or terminals.
Step-by-step instructions for checking a relay with a multimeter
The testing process begins with dismantling the relay. It is located in a box on the side of the compressor and is usually secured with a bracket or clip. After removing the protective cover, disconnect the wire connectors. Pay attention to their location so as not to confuse the contacts during assembly.
For electromagnetic relays, the testing algorithm is as follows:
1. Visually inspect the contacts inside the housing. They must be clean, free of carbon deposits and oxides.
2. Shake the relay near your ear. If a rattling sound is heard, it means that the mechanism is damaged or the contacts are loose - replacement is required.
3. Set the multimeter to resistance measurement mode (Ohm).
4. Call your contacts. The resistance between the input and output should be close to zero (short circuit) if the relay is working properly and is in the operating position.
For posistor relays, the procedure is slightly different. Here it is important to check the resistance of the posistor itself. It should be several tens of ohms (usually from 10 to 50 ohms, the exact values depend on the model). If the multimeter shows infinity (open circuit) or zero (short circuit), the element is faulty.
☑️ Relay diagnostic checklist
Pay special attention to checking the thermal relay. It is often built into the overall design. Check the bimetallic strip for deformation. The resistance between the contacts of the thermal relay in a cold state should be zero (the circuit is closed). If the circuit is open on a cold relay, it has burned out.
An important point is to check the contacts for burning. Even if the electrical parameters are normal, carbon deposits on the contacts increase the resistance, which leads to a voltage drop on the starting winding and the inability to start the engine.
| Relay type | Normal resistance | Fault symptom | Action |
|---|---|---|---|
| Electromagnetic | Close to 0 Ohm (closed) | Infinity or bounce | Replacing or cleaning contacts |
| Posistor | 10–50 Ohm | 0 Ohm or infinity | Replacement only |
| Thermal | 0 Ohm (in cold condition) | Infinity on cold | Replacement of thermal relay |
| Combined | Depends on a pair of contacts | Inconsistency with the diagram | Replacing the entire unit |
If after checking it turns out that the relay is working, but the compressor does not start, the problem may be in the engine itself or in the control system (thermostat, module). In this case, a more in-depth diagnostic will be required with measuring the starting currents.
What to do if you don’t have a multimeter at hand?
If there is no measuring device, you can try to carefully start the refrigerator without a relay (only for experienced ones!). To do this, voltage is briefly applied to the starting winding. If the compressor starts and runs, the relay is faulty. If it hums and stops, the problem is in the compressor. The method is dangerous due to electric shock and requires skills!
Replacing a faulty relay: selection of analogues
If diagnostics showed that the relay in the refrigerator Posis is faulty, it must be replaced. It makes no sense to repair burnt windings or change posistors in makeshift conditions - the reliability of such a repair will be low, and the cost of a new part is low.
When buying a new relay, it is critical to take into account the markings of the old device. Relays are selected not only by the brand of the refrigerator, but also by the power and type of compressor. There is always a code on the body of the part (for example, P-3, P-4, 17.103.04, etc.).
Basic selection rules:
- 🏷️ Matching markings: it is ideal to find exactly the same article number.
- ⚡ Power: the new relay must match the power of your compressor (indicated on the motor nameplate).
- 🔌 Mounting type: make sure that the connectors and mounting method match.
Universal relays (for example, series RTK or R-3) are often suitable for many refrigerator models Pozis, but before installation it is better to check the compatibility table or a consultant. An incorrectly selected relay may either not start the compressor or not protect it during overload.
The installation process is simple: the new device is put on three pins of the compressor (common, starting, working) in the correct position (usually the marking UP should face up). Then the wires are connected according to the diagram or photograph made earlier.
⚠️ Attention: When installing the relay, make sure that the arrow or the inscription "UP" is pointing straight up. An inverted relay will not work correctly, since the moving core will not be able to lower under the influence of gravity to open the starting winding.
After installation, assemble the casing, secure the panel and turn on the refrigerator. The first start can take up to 3-5 minutes (the posistor cooling time or the thermostat delay). If the compressor started smoothly and after some time cold appeared in the chambers, the repair was successful.
Common mistakes when doing your own repairs
Independent repair of refrigerators is a process that requires care. Even a simple relay replacement can be done incorrectly if you do not know some of the nuances. Often, users make mistakes that lead to repeated breakdowns or failure of more expensive units.
One of the main mistakes is ignoring the cleanliness of the contacts. An attempt to install a new relay on oxidized or burnt compressor terminals will lead to poor contact, heating and rapid combustion of the new part. Always clean the contacts on the motor pins with fine sandpaper before installation.
Another common problem is incorrect orientation of the relay in space. As already mentioned, the top-bottom position is critical for electromagnetic relays. Installing the relay sideways or upside down will disrupt the logic of the moving core.
Also, users often confuse the wires when connecting. In three-pin connectors, it is important not to confuse phase, neutral and ground, as well as winding contacts. An error here can lead to a short circuit.
Sometimes, faced with difficulties, craftsmen try to “loop” the relay by sending current directly to the windings. This absolutely cannot be done without special knowledge. The starting winding should turn off within a split second after starting. If it remains on, the engine will burn out in a matter of minutes.
Prevention and extension of service life
To ensure that the relay and compressor of your refrigerator Posis served for a long time, it is important to follow the operating rules. Frequent power surges in the network are the main enemy of electronics and starting equipment. Installing a voltage stabilizer or at least a surge protector will help protect your equipment.
Regular cleaning of the rear wall of the refrigerator from dust is also necessary. Dust, settling on the compressor and relay, acts as a heat insulator, interfering with cooling. Overheating reduces the life of the thermal relay and winding insulation.
You should not often open and close the door unnecessarily, creating excess load on the motor. It is also important to ensure that the refrigerator is level, without distortions, which is especially important for the proper operation of the compressor oil system and relay mechanics.
If you notice that the refrigerator has started to work louder or the switching cycles have become more frequent, do not wait for it to stop completely. Early diagnostics described in this article will help identify the problem at a stage when repairs are minimal and inexpensive.
Is it possible to fix a burnt-out relay yourself?
Theoretically, you can only replace the posistor or clean the contacts, but practice shows that such measures give a temporary effect. The cost of a new relay is low, and the risk of repeated failure or damage to the compressor is high. Therefore, experts recommend a complete replacement of the unit.
Why does the relay heat up during operation?
Slight heating of the relay body is normal, since current passes through it. However, if the case becomes so hot that it is impossible to touch it, this is a sign of a malfunction (poor contact, incorrectly selected power or problems with the compressor).
How often do you need to change the relay in the Pozis refrigerator?
The relay does not have a scheduled replacement period. With normal operation and stable mains voltage, it lasts as long as the compressor itself (10-15 years or more). Replacement is required only when signs of malfunction appear.
Where to find the relay markings?
The marking is applied to the side or top edge of the plastic relay case. To see it, it is not necessary to completely remove the part; just pull back the compressor protective casing. Look for a combination of letters and numbers (for example, P-3, 3.3).