A sudden stop of the refrigerator or its inability to maintain the set temperature often frightens owners, but in many cases the problem lies hidden in compressor or adjacent elements of the circuit. Before calling a professional, it is worth conducting basic diagnostics to understand the scale of the disaster. The engine is the heart of the system, and its health is critical for refrigerant circulation.
However, do not rush to conclusions. Sometimes electronics or thermostat malfunctions are mistaken for engine failure. In this article we will look at how check the start relay to do it yourself compressor without complex equipment. This will help you save time and money if the repair turns out to be simple.
The first step should always be a visual and auditory assessment of the condition of the unit. If the refrigerator hums but does not freeze, or makes loud clicks and goes silent, these are direct signs of problems in the motor electrical circuit. Pay attention to body vibration and the nature of the sounds when you try to start.
A frequent cause of failure is not the motor itself, but the protective starting relay. It is responsible for supplying voltage to the windings at the moment of start. If this element burns out, the engine simply will not start, although it may be fully operational. It is also worth inspecting the wiring for melting or oxidation of the contacts.
⚠️ Attention: Before starting any diagnostic work, be sure to disconnect the refrigerator from the electrical network! Working with electrical appliances under voltage is deadly.
There are several ways to determine the condition of the motor. The simplest is to check winding resistance with a multimeter. A more complex method requires checking starting current, but it is only available to experienced craftsmen with the appropriate equipment.
Primary diagnostics: sounds and external signs
Before you take up the tools, listen carefully to what is happening inside the unit. A characteristic sound that turns into silence after a few seconds indicates that the engine is trying to start, but cannot. This often indicates a jammed piston group or a problem with the starting device. humturning to silence after a few seconds indicates that the engine is trying to start but cannot. This often indicates a jammed piston group or a problem with the starting device.
If you only hear the quiet hum of the transformer or electronics, and the motor is silent, perhaps the voltage simply does not reach it. In this case, it is worth checking thermostat the power circuit as well. The absence of any sounds when plugged in may indicate a broken plug or cord.
It is important to distinguish between normal operating noise and alarm signals. Light vibration and a uniform hum are normal. However, an intermittent Jerky operation motor or a loud metallic knock requires immediate stop of the device. Ignoring these symptoms can lead to complete failure of the cooling system.
Checking the starting relay and protective thermal contact
The most common cause of a “silent” compressor is a malfunction of the starting relay. This small plastic block attaches to the side or bottom of the engine. Inside it there is a coil and contacts that can burn or stick. To check it, you must carefully remove it, having first photographed the connection diagram.
Visual inspection often gives the answer: if soot, melted plastic is visible inside the plastic, or a burning smell is felt, the part requires replacement. Also check the integrity thermal protectionwhich is often built into the same structure or located nearby.
- 🔌 Disconnect the wires from the relay, remembering their location.
- 👀 Inspect the contacts for the presence of carbon deposits or oxidation.
- 🔊 Shake the relay near your ear: if a ringing is heard, it means the internal mechanical part is destroyed.
- 🧪 Ring the circuit with a multimeter in resistance test mode.
⚠️ Attention: Starting relays come in different types (inductive, posistronic). When purchasing a new part, make sure that it matches your engine model, otherwise the motor will burn out.
If the relay is working properly, the problem may lie in the engine itself or the supply wires. Make sure contacts the motor terminals are not oxidized. If necessary, sand them with fine sandpaper. Poor contact creates additional resistance, which interferes with normal start-up.
☑️ Diagnostics of relays and contacts
Diagnostics of motor windings with a multimeter
The most reliable way to check the electrical part of the motor is to measure winding resistance. For this you will need a multimeter. On the body of most compressors there is a diagram or marking of the terminals: Common (C), Start (S) and Run (R). They are usually arranged in a triangle.
In resistance measurement mode (Ohm), ring pairs of contacts. There must be a certain resistance between the common point (C) and the starting point (S), as well as between the common point (C) and the working point (R). If the device shows infinity (open) or zero (short circuit), the engine is faulty.
| Pair of contacts | Normal resistance | Possible malfunction |
|---|---|---|
| Common - Working (C-R) | 10 - 25 Ohm | Interturn short circuit or open circuit |
| Common - Starting (C-S) | 20 - 40 Ohm | Malfunction of the starting winding |
| Working - Starting (R-S) | Sum of the two previous ones | Failure of the circuit inside the engine |
| Case - Any contact | Infinity (∞) | Breakthrough to the case (dangerous!) |
Pay special attention to checking for a breakdown to the housing. Press one multimeter probe to the cleaned area on the compressor housing (where there is no paint), and touch each of the three terminals with the other. The device should show infinity. Any resistance value indicates that the engine shorts to groundand cannot be operated.
Why is the resistance of the windings different?
Starting the winding always has greater resistance, since it is made of thinner wire and is intended only to create a short-term magnetic field at startup. The working winding is thicker and has less resistance for constant operation.
Checking for interturn short circuit and wedge
If the resistance of the windings is normal, but the engine still does not start or the machine knocks out, it is possible turn-to-turn short circuit. This is a defect in which the insulation between the turns of the coil is broken. The multimeter may not show it, since the resistance will change slightly, but when voltage is applied, the current will increase sharply.
For accurate diagnostics, professionals use current clamps. When starting, a working engine consumes a current corresponding to its power (usually 0.5–1.5 A for household models). If the current jumps to 3–5 A and the protection immediately trips, there is a short circuit. This may also indicate mechanical wedge piston group.
- 📉 Resistance drop windings when heated - a sign of short circuit.
- ⚡ Current surge at start above the nominal value by 2-3 times.
- 🔥 Fast heating compressor housing to a scorching temperature.
Mechanical wedge often occurs due to oil production or the ingress of foreign particles. In this case, the motor shaft cannot turn. Sometimes the “wedging” method by applying increased voltage helps, but doing this at home is strictly not recommended due to the risk of fire.
⚠️ Attention: If you find a breakdown in the housing or an interturn short circuit, further operation of the refrigerator is prohibited. This can lead to electric shock or fire in the wiring.
Analysis of motor operation under load
Sometimes the engine starts and even freezes, but does not work correctly. For example, it may not turn off for hours or work in cycles with very short pauses. This indicates a loss performance. The compressor pumps, but does not create the required pressure in the system.
You can check this by measuring the temperature in different areas. The discharge tube (compressor outlet) should be hot and the suction tube should be cold or frosted. If both tubes have the same temperature, the capillary may be broken system tightness or clogged.
It is also worth paying attention to the noise level. The appearance of new sounds: gurgling, hissing or metallic clanging indicates a change in the nature of the work piston group. In such cases, replacing the engine is often the only way out, since repairing the old one is not economically feasible.
When it is necessary to replace the compressor
The decision to replace the engine should be made after a comprehensive check. If the windings are broken, there is a breakdown in the housing, or a mechanical wedge is confirmed, repair is impossible. Replacement is also required if compressor it has lost its seal and oil has come out of it.
It is important to choose an analogue with identical characteristics: power, refrigerant (R134a, R600a) and oil type. Installation an unsuitable motor will lead to rapid breakdown of a new part or ineffective operation of the refrigerator.
- 🛠️ Dismantling old compressor using a pipe cutter.
- 🧹 Purge the system nitrogen for removal of combustion products.
- 🔧 Installation new motor and filter drier.
- ❄️ Refilling refrigerant and evacuation of the system.
Remember that replacing a compressor is a complex process that requires special equipment (vacuum pump, pressure gauge station, burner). It is almost impossible to carry out this operation independently without skills and tools, so at this stage it is better to turn to professionals.
Is it possible to use a compressor from another refrigerator?
It is possible if the type of refrigerant, power and overall dimensions are the same. However, it is better to look for the original model or its direct analogue in the manufacturer’s catalog.
Why does the refrigerator motor get very hot?
Strong heating (up to 80-90°C) may be the norm for some models, but if the body burns your hand, this is a sign of overload. Reasons: contamination of the condenser at the back, freon leak, malfunction of the thermostat or wear of the engine itself.
Is it possible to repair a burnt-out compressor?
In domestic conditions - no. Rewinding the windings requires factory equipment, and opening the housing breaks the seal. The only way is to replace the entire unit.
How often do you need to change the compressor?
The service life of a modern compressor is 10-15 years. With proper operation and stable mains voltage, it can work longer. Frequent breakdowns are usually associated with power surges or refrigerant leaks.
Is it dangerous to check the engine yourself?
Checking with a multimeter with the power off is safe. However, attempting to start the motor directly or under high voltage without protection may result in injury or fire.