The situation when the refrigerator stops cooling, and there is deathly silence inside or, conversely, a humming sound without starting, is familiar to many owners of household appliances. Most often, suspicion falls on compressor the heart of the cooling system, which circulates the refrigerant. Before calling a technician or buying a new unit, it is important to carry out competent initial diagnostics to understand whether the problem is really in the motor, or whether the start relay or thermostat is to blame.
Checking the compressor directly is an effective way to eliminate damage to the control electronics and ensure the integrity of the electrical circuit of the engine itself. However, it is worth remembering that working with high voltage requires strict adherence to safety precautions. In this article we will analyze detailed action algorithms, the necessary tools and interpretation of the obtained measurement results.
Is it worth immediately disassembling the equipment at the first sign of a malfunction? No, first you need to conduct an external inspection and listen to the sounds of operation. Sometimes the problem is solved by replacing an inexpensive relay, rather than by complex motor repairs. Understanding the principle of operation single-phase asynchronous motor will help you avoid unnecessary costs.
Visual diagnostics and initial inspection
The first stage is always a visual assessment of the condition of the unit without dismantling unnecessary parts. You need to unplug the refrigerator, move it away from the wall and gain access to the back where the motor-compressor is located. Pay attention to the appearance of the housing: there should be no traces of oil, severe corrosion or mechanical damage.
Inspect the wires going to the compressor. If the insulation is melted or traces of a short circuit (black soot) are visible, this may indicate overheating or breakdown. It is also important to check the condition of the start relay, which is usually mounted on the side of the compressor. If the relay makes a rattle sound when slightly shaken, most likely its internal contacts are damaged.
Plug in the refrigerator (being careful) and listen. If you hear a distinctive clicking sound, followed by a buzzing sound that lasts 5-10 seconds, and then a clicking sound that turns off, this is a classic symptom. The engine tries to start, but starting winding does not receive the required impulse or the rotor is jammed. If there is complete silence, the problem may be a lack of power or an open circuit.
⚠️ Attention: If you find traces of oily smudges on the compressor housing in the area of the welds or tubes, this may indicate not only a loss of freon, but also a violation of the tightness. It is dangerous to operate such a unit, as the oil may ignite upon contact with hot parts.
Do not ignore the burning smell. If you notice a strong smell of burning plastic or insulation when you turn it on, immediately turn off the power to the device. This is a sure sign that there is a short circuit inside the windings or the starting device has burned out. Further attempts to start up may lead to complete failure of the unit.
Necessary tools for testing
For high-quality diagnostics, you will need a minimum set of tools that most home craftsmen can find. Without special equipment, it is impossible to carry out an accurate check, since a visual inspection does not provide a complete picture of the condition of electrical circuits.
The main device in your arsenal will be multimeter (or tester). It is necessary to measure the resistance of the windings and check for a breakdown on the housing. Make sure that the device is working properly and that its probes have intact insulation. You will also need a screwdriver to remove the protective casing and terminal box.
- 🔧 Multimeter with the function of measuring resistance (Ohm) and continuity
- 🪛 Set of screwdrivers (phillips and flat) for removing the casing
- 🔌 Straight wires with clamps ("crocodiles") for supplying voltage
- 🧤 Dielectric gloves for protection against electric shock
To directly supply voltage to the windings, if you decide to conduct such a test, you will need two insulated wires with a plug. One of them must have a switch or button to briefly close the circuit. The use of homemade twists without insulation is strictly prohibited by electrical safety rules.
If you do not have a multimeter, you can use a simple test light, but this method is less accurate and will not show the exact resistance of the windings. The light will only indicate the presence or absence of contact, which in the case of complex diagnostics asynchronous motor may not be enough.
Removing the protective casing and access to the contacts
To get to the electrical part of the compressor, you need to remove the protective plastic or metal casing located at the lower rear of the refrigerator. It is usually secured with latches or screws. Be careful, the plastic becomes brittle over time and may crack.
After removing the casing, you will see the compressor itself - a black metal “tank”. On its body there is a terminal box, often closed with an additional plastic cap. This is where the contacts for connecting the starting relay and the working winding are located.
Remove the starting relay. It fits directly onto the three terminals of the compressor. Carefully disconnect the wires going to the relay and remove it from the motor terminals. Now in front of you are three pins arranged in a triangle. These are the terminals of the windings: common, starting and working.
☑️ Check before disassembly
It is important not to confuse the conclusions, although this is not critical for the initial check of the integrity of the windings. However, if you plan to test the operation of the motor under voltage, you need to know exactly which pin does what. The location diagram is usually marked on the compressor or relay itself.
Measuring winding resistance with a multimeter
The most reliable way to check the electrical part is to measure the resistance between the terminals. Switch the multimeter to resistance measurement mode (200 Ohm or 2 kOhm range). First check the resistance between pairs of terminals. Typically, a working compressor has a resistance between the working and common terminals of 10-30 Ohms, and between the starting and common terminals - 20-40 Ohms.
The resistance between the working and starting terminals should be the sum of the two previous values. If the device shows infinity (open) or zero (short circuit) in any of the pairs, the compressor is faulty. A break indicates a winding burnout, and a zero indicates an interturn short circuit.
Pay special attention to checking for breakdown of the housing. Switch the multimeter to dial mode (with sound) or maximum resistance measurement. Press one probe against any of the three terminals, and touch the other to a cleaned area on the metal body of the compressor (where there is no paint). The device should not respond.
| Pair of contacts | Normal resistance | Symptom of malfunction |
|---|---|---|
| Working - General | 10 - 30 Ohm | Open circuit or short circuit |
| Starting - General | 20 - 40 Ohm | Open circuit or short circuit |
| Working - Starting | Sum of two above | Inconsistency with the amount |
| Any output - Housing | Infinity (∞) | Breakdown to the housing |
If the multimeter readings differ from normal, further operation refrigerator is not possible. A motor with incorrect winding geometry will operate inefficiently, overheat and may cause a fire. In this case, the unit needs to be replaced.
Why is the resistance of the starting winding higher?
The starting winding is made with a thinner wire and has more turns to create the necessary phase shift to start the engine. Therefore, its resistance is always higher than that of the working winding, which is designed for long-term operation under load.
Checking the compressor by direct connection to the network
If the electrical parameters of the windings are normal, but the motor does not start, you can try to apply voltage directly, bypassing the start relay and thermostat. This method allows you to determine whether engine get in motion at all. To do this, assemble a circuit: the power plug is connected to the common and working terminals, and the starting terminal is briefly connected to the working terminal.
Be extremely careful: there will be a voltage of 220 Volts on the wires. Wear dielectric gloves, hold the wires only by the insulation, and the compressor itself should not touch metal objects. Briefly (for 1-2 seconds) close the starting winding circuit to give an impulse, and immediately break the contact.
If the compressor is working properly, you will hear a confident hum, and air will come out of the outlet tube. If the motor hums, but does not spin, or knocks out the breakers in the shield, there is a mechanical wedge or a strong interturn short circuit. In this case, repair is not economically feasible.
⚠️ Attention: Long-term operation of the compressor without a connected capacitor or starting relay (in circuits where it is necessary) is prohibited. The motor can burn out in a few seconds due to lack of proper phase shift. Use this method only for short-term diagnostics!
After successful startup, check whether the compressor is sucking in air at the inlet and blowing out air at the outlet. Place your finger on the suction tube - you should feel a slight suction. A strong stream of air should be felt on the discharge tube. The lack of pressure indicates an internal failure of the valve group.
Typical malfunctions and their symptoms
Understanding the symptoms helps to quickly diagnose the problem. For example, if the compressor runs continuously without turning off, but there is no cold, this may indicate a freon leak or loss of performance of the motor itself. In such cases, the pressure in the system does not reach the values required to turn off the thermostat.
A frequent problem is an interturn short circuit. It manifests itself in the fact that the motor hums louder than usual, gets very hot and after a while the thermal relay turns off. The multimeter may show normal resistance, since a short circuit occurs only under load when heating.
- 🔊 Humming and clicking without starting - the starting relay is faulty or the piston is jammed
- 🌡️ Strong heating of the case - interturn short circuit or lack of refrigerant
- 🔇 Complete silence - open circuit, burnt-out thermostat or lack of power
An “oil wedge” is also found when the compressor stood idle for a long time, and the oil flowed into the crankcase, forming a plug. In this case, sometimes carefully warming up the case (not with an open fire!) helps, but most often the unit needs to be replaced.
Safety and precautions
Working with live electrical appliances always carries risks. The main rule: never touch live parts with your bare hands. Even if you use tools with insulated handles, it doesn't hurt to be on the safe side. Always check the integrity of the wire insulation before connecting.
The compressor contains refrigerant that is under pressure. It is strictly forbidden to cut the tubes or open the compressor housing without special equipment to collect freon. This is not only dangerous (risk of explosion or suffocation), but also illegal from an environmental point of view.
If you are not confident in your abilities or do not have experience working with electricity, it is better to entrust the diagnosis to professionals. An error in the connection can lead to electric shock or fire in the wiring in the apartment.
Frequently asked questions (FAQ)
Is it possible to repair a burnt-out compressor?
It is impossible to rewind the compressor windings at home. Special equipment is required for vacuuming and charging with freon. It is easier and more reliable to replace the unit with a new or used one in working condition.
Why is the compressor hot to the touch?
Heating up to 70-90 degrees for a working compressor is the norm. However, if it is so hot that it is impossible to touch it, or heats up in seconds, this is a sign of a malfunction (wedges, short circuit, lack of freon).
How to distinguish a compressor breakdown from a freon leak?
If the compressor works continuously, but there is no cold, and at the same time it is not hot (or warm), most likely there is a leak Freon. If the engine is hot, hums and turns off, the problem is in it or in the starting system.
How much does it cost to replace a compressor?
The cost consists of the price of the unit itself and the work of the technician. On average, this can range from 30% to 60% of the cost of a new refrigerator, so it is often more advisable to buy new equipment.