The situation when the refrigerator stops working cold, often takes you by surprise, and the first suspicion is engine failure. However, before calling a technician or buying a new unit, it makes sense to conduct an initial diagnostic compressor. In most cases, the problem lies not in the engine itself, but in the start relay or thermostat, which you can fix yourself. Understanding the principle of operation of the electrical circuit allows you to save significant money on the repair of household appliances.
Direct connection to a 220 volt network is a radical but effective method of checking the performance. electric motor. If, when voltage is applied directly, the shaft begins to rotate and a characteristic hum appears, it means that the windings are intact, and you need to look for a fault in the control system.
In this article we will look in detail at how to safely remove the compressor, test the windings with a multimeter and assemble a temporary circuit for starting. You will learn how to distinguish the starting winding from the working winding and why starting relay often becomes the culprit of equipment downtime. Following the algorithm of actions will help to accurately determine the cause of the breakdown.
⚠️ Attention: Carry out all manipulations with the electrical part of the refrigerator only with the device completely disconnected from the network! Accidentally plugging into a socket during disassembly can lead to electric shock.
Diagnostics of faults before direct start-up
Before disassembling the equipment, it is necessary to localize the problem. If the refrigerator hums but does not start, or, conversely, is silent, these are different scenarios. The first step is to check the integrity of the power cord and the presence of voltage in the outlet. Users often forget about such trivial things as broken plugs or oxidized contacts.
Next you should inspect thermostat. If you do not hear a characteristic click when you turn the temperature control knob, the contact may be open. In some models, for example Indesit or Atlant, the thermostat can be easily removed and checked by dialing. Lack of response to changing the temperature settings indicates the need to replace this element.
Pay special attention to the appearance of the compressor. If traces of oil are visible on the housing, it means that the freon circuit has depressurized. In this case, it is strictly forbidden to start the engine, since it operates in an oil environment, and the lack of refrigerant will lead to overheating. Also check the condition of the tubes: they should not be deformed or have cracks.
- 🔍 Check the integrity of the electrical cable and plug.
- 🔊 Listen to the sounds: humming without starting or complete silence.
- 🌡️ Assess the operation of the thermostat and the presence clicks.
- 💧 Inspect the compressor for oil leaks.
⚠️ Attention: If you find mechanical damage to the tubes or traces of oil on the motor housing, further self-diagnosis without vacuuming and filling the system is useless and dangerous.
Necessary tools and safety measures
To carry out high-quality diagnostics, you will need a minimum set of tools, which most home craftsmen can find. The main device will be multimeter (tester), which allows you to measure the resistance of the windings and check the integrity of the circuit. Without this device, diagnostics will be only approximate.
You will also need pliers, side cutters and insulating tape. For a temporary connection, a piece of wire with a plug is often used. It is important that the wire cross-section matches the power consumption of the motor, usually at least 0.75 mm². Poor insulation or thin wire can cause a short circuit.
Ensure the work area is well lit. The compressor is located in a niche at the back of the refrigerator, where dust and cobwebs often accumulate. Before starting work, it is recommended to vacuum the area around the motor so that dirt does not get inside the electrical contacts when removing the casing.
☑️ Preparation for diagnostics
Removing the protective casing and dismantling the relay
The process begins with removing the protective box covering the compressor. It is usually secured with latches or bolts. In models Bosch i Siemens the casing can be combined with a decorative panel that requires careful handling. After removing the protection, access to the electrical part opens.
At the end of the compressor you will see a plastic box - this is the starting relay. It is responsible for starting the engine and switching the windings. The relay simply slides onto the three contact studs of the compressor and is secured with a bracket or spring clip. Carefully remove the bracket and pull the box down.
Inside the relay there is a starting capacitor and a switching mechanism. Visually inspect the contacts: if they are blackened or melted, the relay must be replaced. However, to check the motor itself, we need to disconnect the relay completely, freeing the three compressor studs. Remember or photograph the position of the wires so that you can correctly assemble the circuit later.
The three pins on the compressor are the common terminal, the starting and working windings. Their correct identification is critical for a successful launch. By mixing up the contacts, you can burn the winding or cause a short circuit.
What's inside the starting relay?
Inside the plastic case there is a coil with a movable core and contacts. When current is applied, the core is retracted, completing the starting circuit. After the motor accelerates, the current drops and the core opens the contacts. Modern models often use a posistor - a ceramic element that changes resistance when heated.
Checking the windings with a multimeter
Before applying voltage, you must “ring” the windings. This will make it possible to identify an interturn short circuit or open circuit, in which direct starting is useless and dangerous. Switch the multimeter to resistance (ohms) measurement mode. First, check the resistance between each pair of studs.
Normal resistance values for household refrigerators range from 10 to 30 ohms for the operating winding and from 20 to 50 ohms for the starting winding. The total resistance between the extreme terminals should be equal to the sum of the resistances of the other two pairs. If the device shows infinity, there is a break; if zero, there is a short circuit.
It is also necessary to check the breakdown on the housing. Touch one probe of the multimeter to any stud and the other to the copper tube or unpainted part of the compressor housing. The device should show infinity. The appearance of any resistance values indicates that the motor is “broken” and cannot be operated.
| Measurement type | Normal value | Failure sign |
|---|---|---|
| Working winding | 10 – 30 Ohm | Open or short circuit |
| Starting winding | 20 – 50 Ohm | Open or short circuit |
| Breakdown to the body | Infinity | Any resistance value |
| Sum of resistances | R1 + R2 = R3 | Sum discrepancy |
⚠️ Attention: If the winding resistance is very different from the norm (for example, 1-2 Ohms or several Mega Ohms), further attempts to start may lead to a wiring fire or final failure of the motor.
Scheme of direct connection to a 220V network
If a check with a multimeter shows the integrity of the windings, we proceed to the most important stage - direct connection. To do this, we need to supply 220 volts to the common terminal and one of the windings (usually the working one) to start the motor. Since we don’t have a start relay in the circuit, we will have to imitate the start function or use a circuit with a button.
Define the common pin. Most often it is located separately from the other two, or the resistance between it and the other two terminals is the least. In the diagrams it is designated as C (Common). Working winding (R) has average resistance, and the starting one (S) has the highest. Connect one wire from the plug to the common terminal.
The second wire from the plug must be briefly applied to the starting winding to create torque, and then switched to the working winding. However, there is a simpler and safer method using a start button or even an old working relay. If the relay is working properly, you can simply connect it to the pins and apply power through it - it will perform the switching itself.
Connection diagram:Phase (L) -> Common terminal (C)
Zero (N) -> Working winding (R) through button/relay
Starting winding (S) -> connected briefly
It is important to fix the compressor before turning on. Without attachment to the frame, it will vibrate violently and may tip over, damaging the tubes. Place the motor on a flat surface with a rubber mat or thick cloth underneath. Make sure there are no flammable objects nearby.
Analysis of results and interpretation of data
After applying voltage, carefully monitor the behavior of the motor. If you hear a confident hum, the shaft rotates, and air comes out of the tubes, the compressor is working. This means the problem was in the relay, thermostat or wiring. In this case, replacing the faulty element will bring the refrigerator back to life.
If the motor hums but does not start, and after a few seconds the machine knocks out or the thermal protection clicks, it means the piston group is jammed. This often happens due to oil burnout or prolonged inactivity. Attempts to “unwedge” such compressors often give a temporary effect, and soon the breakdown recurs.
The absence of any sounds when voltage is applied indicates an open circuit inside the motor or a lack of contact. Check the connection diagram again and the reliability of the connection of the wires with the studs. Oxidized contacts can prevent the passage of current even with serviceable windings.
- 🟢 A confident hum and pressure in the tubes - the motor is working properly.
- 🔴 Hum, heating and shutdown of the protection - jamming of the compressor.
- ⚫ Full silence - open circuit or lack of contact.
- 🔥 Sparking and burning smell - short circuit of the windings.
⚠️ Attention: Do not keep the compressor turned on directly for more than 5-7 minutes. The standard cooling system of the motor in the refrigerator is tied to the circulation of freon and the operation of the fan (in NoFrost), so in the open air it overheats faster.
Frequently asked questions and answers
Can the refrigerator be left to work with a directly connected compressor?
No, this is unacceptable. Direct connection is used for short-term diagnostics only. Without a starting relay and thermal protection, the motor will quickly overheat, which will lead to a fire or permanent breakdown. Operation is possible only with a standard or similar protection system.
Why does the compressor hum, but does not start without a relay?
A single-phase motor needs a phase shift to start, which is created by the starting winding. Without briefly connecting the starting winding (or using a capacitor/relay), the magnetic field is not enough to rotate the rotor, and the motor only hums while in a inhibited state.
How to determine which winding is the starting winding and which is the working one?
Measure the resistance between the studs. The winding with higher resistance is the starting winding, and the winding with lower resistance is the working winding. The overall conclusion lies at the intersection of these dimensions. In some models LG or Samsung the circuit may differ, it is better to check the technical documentation.
Is it dangerous to check the compressor without evacuation of the system?
To check the electrical part (spinning or not), evacuation is not required. However, if you plan to solder a new compressor, then soldering work should be carried out only after pumping out the freon and filling the system with nitrogen in order to avoid ignition of the oil inside the circuit.