Sudden stoppage of operation of the refrigerator or an uncharacteristic hum from the compressor often indicates problems in the electrical circuit. One of the key elements that ensures engine starting is start-up relay. It is this that supplies the impulse to the starting winding and protects the motor from overloads. If this component fails, the refrigerator stops cooling, although the light inside is on.
Before calling a technician or buying new equipment, it is worth conducting an initial diagnosis. Often the cause of the breakdown lies precisely in a burnt out or stuck relay, the replacement of which is inexpensive and can be done independently if you have basic skills. In this article we will look at how to check the relay for functionality on a refrigeratorwhat tools will be needed and what to pay special attention to during a visual inspection.
Timely detection of a malfunction will help to avoid more serious problems, such as combustion of the compressor windings. The trigger mechanism is a consumable item that wears out over time. Understanding the principle of its operation and signs of failure will allow you to quickly determine whether an urgent replacement is required or whether the problem lies deeper.
Signs of a faulty start-up relay
You can determine that the relay has failed by characteristic external signs, without immediately resorting to complex tools. The most obvious symptom is that the compressor tries to start, makes a clicking sound, hums for a few seconds, and then there is a clicking sound and silence again. This phenomenon is called “humming without starting” and indicates that starting winding does not receive the necessary impulse or the protection is instantly triggered.
Another alarming signal is the frequent disconnection of the refrigerator from the network by the thermal protection relay. If the motor housing becomes excessively hot and the unit operates with short cycles, the contacts inside the relay may be stuck closed or, conversely, oxidized and not conducting current. In some cases, you can hear a crackling sound or smell a burning smell in the compressor area.
⚠️ Attention: If after the relay clicks and an attempt to start the compressor is silent, and after 10-15 minutes another click is heard, do not leave the refrigerator plugged in under any circumstances. This can lead to overheating and seizure of the engine piston group.
Visual inspection can also provide a lot of information. If you remove the casing and inspect the relay, you may notice blackening of the housing, melting of the plastic or traces of soot on the contacts. Thermal protection in such cases it often has visible damage.
The design and principle of operation of the relay
To carry out high-quality diagnostics, you need to understand how this node works. In modern household refrigerators, two types of devices are most often found: electromagnetic and posistor. Electromagnetic relay works due to the current passing through the winding, which creates a magnetic field that draws in the core and closes the starter contacts.
Posistor models that often called “pills”, they work based on the properties of a semiconductor material. When voltage is applied, the posistor heats up, its resistance increases sharply, and the starting winding circuit opens. After cooling (usually 3-5 minutes), the resistance drops and the cycle can repeat. That is why the refrigerator pauses when it is turned on and off frequently.
The design of any relay includes input contacts for connecting to the network and output contacts for connecting to the compressor windings. There is also a mechanism inside that opens the circuit in case of overcurrent. Bimetallic plate bends when heated and breaks the contact, protecting the motor. Understanding these differences is important, since the methods for testing them may differ slightly.
What is the difference between relays from different manufacturers?
Electromagnetic relays are often marked RTK (Russia) or R (European), they are noisier during operation. PTC (posistor) devices operate silently, but are sensitive to voltage surges and require time to cool down before restarting.
Removing the relay for inspection
Checking the relay is impossible without removing it from the compressor housing. Before starting work, be sure to disconnect the refrigerator from the power supply! This is a safety requirement and, if ignored, may result in electric shock. Remove the rear panel of the unit to gain access to the motor.
The relay is usually placed on three contacts of the compressor and secured with a bracket or plastic latches. Carefully remove the retaining bracket and pull the device down. If it does not budge, do not use excessive force; wires or fasteners may be in the way. Disconnect the wires, first remembering or photographing their location.
☑️ Safe removal of the relay
After removal, carefully inspect the device. Shake it near your ear: if a rattling sound is heard inside, it means the contacts or internal elements are damaged. This is a 100% sign of a malfunction. Also check the condition of the contact pads on the compressor itself - they should be clean and not oxidized.
| Relay type | Location | Characteristic sound | Check feature |
|---|---|---|---|
| Electromagnetic | Side, vertical | Loud click | Checking the coil for resistance |
| Posistor | Side or top | Silence or quiet click | Checking the resistor resistance |
| Thermal | Inside the relay housing | Absent | Checking the circuit in cold condition |
Checking the relay with a multimeter
The most accurate diagnostic method is to use a multimeter (tester). Switch the device to resistance measurement mode (Ohms). First, check the integrity of the thermal release circuit. The probes are applied to the input and output contacts. The device should show zero or a value close to it. If the screen shows “1” or “OL”, the circuit is open, the relay is faulty.
Next, we check the starting part. For electromagnetic relays, the coil resistance should be in the range of 3-10 Ohms (depending on the model). If the resistance is too high - a break; if it is close to zero - a short circuit of the turns. For posistor relays the normal resistance at room temperature is 15-50 Ohms. If the posistor “rings” like zero or does not ring at all, it must be replaced.
It is important to check whether the contacts open when heated (for thermal relays). This can be done by gently heating the element with a hairdryer (not open fire!), and monitoring the resistance. The chain must break. However, at home it is easier to replace a suspicious thermal relay, since it is inexpensive, and its incorrect operation is dangerous for the motor.
Diagnostics without instruments
What to do if you don’t have a multimeter at hand? There is a method of checking “by ear” and by indirect signs, although it is less accurate. Take the relay in your hand and shake vigorously. As already mentioned, rattling inside is a sign of destruction. If something is loose inside, the device will not work.
You can try to apply voltage directly, but this method requires extreme caution and understanding of electrical circuits. For a short time (for 1-2 seconds!) you can apply 220V to the working winding of the compressor. If the motor starts and hums smoothly, then the problem is in the starting device. Never leave the compressor on without a starting relay for more than 2-3 seconds - this will lead to burnout of the windings!
You can also use the method of replacing it with a known-good relay. If you have an old but working relay from another refrigerator (with similar characteristics), install it. If the refrigerator starts and starts freezing, the diagnosis is confirmed. This method is often used by service center technicians to quickly localize the problem.
⚠️ Attention: Direct connection of the compressor to the network without a start relay is only permissible for short-term diagnostics of the health of the motor itself. Operating the refrigerator without protection is prohibited and is a fire hazard.
Replacing and selecting a new relay
If the diagnostics showed a malfunction, the relay must be replaced. The selection of an analogue is carried out according to the markings indicated on the body of the old device. The main parameters are: current strength (for example, 1/4 HP, 1/5 HP or in Amps), type of compressor (low-, medium- or high-pressure) and contact arrangement (vertical or horizontal).
When installing a new device, make sure that the marking UP or the arrow points up. This is critical for proper operation of the thermal release and posistor. Incorrect orientation will result in the protection not working in case of overheating, or the start-up will be unstable. Push the relay onto the compressor contacts until it stops and secure with a bracket.
After assembly, turn on the refrigerator. It is normal for the compressor to start within 1-5 seconds after the click. If the startup was successful, let the unit run for 15-20 minutes and check the heating of the relay housing. It may be warm, but it should not burn your hand or spark.
Frequently asked questions (FAQ)
Is it possible to repair a burnt-out relay yourself?
In most cases, repair is impractical. Inside there are calibrated elements (posistor, bimetallic plate) that cannot be restored at home. It’s easier and safer to buy a new set.
Why does the new relay immediately burn out?
This may indicate problems with the compressor itself (turn-to-turn short circuit), voltage surges in the network, or incorrect selection of the relay model for the current. Also, the cause may be a jammed engine piston.
How often do you need to change the relay?
The service life of the start-up relay is 5-10 years. However, with frequent power surges or unstable network operation, it may fail earlier. Planned replacement is not required, only after a breakdown.
Does the room temperature affect the operation of the relay?
Yes, posistor relays are sensitive to temperature. In a very cold room, the readiness time to restart may be longer. In hot weather, the thermal release can operate faster.