The situation when the refrigerator stops cooling and the temperature inside rises always takes you by surprise. Often the first sign of a serious breakdown is the silence of the motor or, conversely, its frantic attempts to start and an instant shutdown. Owners of household appliances often wonder how to understand what exactly has gone wrong: complex control electronics, a starting relay, or itself, which is the heart of the entire system. Self-diagnosis allows you to save time and money on calling a technician for an initial inspection. compressor, which is the heart of the entire system. Self-diagnosis allows you to save time and money on calling a specialist for an initial inspection.
Checking the refrigerator compressor directly without a relay is an effective method that allows you to isolate the electric motor from the auxiliary elements of the circuit. If the motor starts when connected directly, then the problem lies in the start-up relay or thermostat. However, this process requires strict adherence to safety precautions, since you will be working with high voltage and exposed contacts. Any mistake can lead to electric shock or the final failure of an expensive unit.
In this material we will analyze in detail the structure of the motor-compressor, the necessary diagnostic tools and a step-by-step algorithm of actions. You will learn how to safely bypass the standard launch circuit and what to pay attention to first. It is important to understand that even if the engine starts, this does not guarantee its full serviceability in the long term, but it will give a clear answer about the need to replace the relay.
The principle of operation and design of the motor-compressor
To successfully carry out diagnostics, you need to understand how the unit you are going to check works. Modern household refrigerators are equipped with hermetically sealed piston compressors. Inside the metal casing there is an electric motor and a compressor part immersed in oil. Electrical energy is supplied to the stator windings, creating a magnetic field that drives the rotor.
The key element for starting is the starting winding. Unlike the working winding, which creates the main torque, the starting winding provides the initial impulse to shift the rotor. As soon as the engine reaches a certain speed, the starting winding must be turned off. This process is precisely controlled starting relay, which we will exclude from the chain when checking. If the relay is stuck or burnt out, the circuit opens and the motor hums, but does not spin.
There are usually three terminals on the compressor housing, forming a triangle. These are the contacts of the working winding (R), the starting winding (S) and the common wire (C). Depending on the manufacturer, for example Atlant, Indesit or LG, the markings and location of the contacts may differ, but the physical principle remains the same. Understanding this circuit is critical for proper wiring when direct voltage is applied.
⚠️ Attention: Inside the compressor casing there is pressurized freon and oil. It is strictly forbidden to open the sealed casing, saw it, or try to disassemble the unit at home. All manipulations are carried out only with the external electrical part.
Necessary tools and safety measures
Before starting work, you need to prepare the workplace and tools. You don't need complex professional equipment, but a basic home craftsman's kit is required. The main requirement is that all tools must be in good working order, and the insulation of the wires must not be damaged.
- 🛠️ Multimeter (tester) for testing windings and checking resistance.
- 🔌 Wires with alligator clips for temporary connection.
- 🔧 Set screwdrivers and pliers for dismantling the casing and terminals.
- 🧤 Dielectric gloves for protection against electric shock.
- 💡 Incandescent lamp (power 100-150 W) for creating a control circuit.
Safety is priority number one. The work will be carried out with a mains voltage of 220 Volts. Before starting any actions, the refrigerator must be completely disconnected from the network. Do not touch metal parts of the housing or compressor while power is applied. You should also make sure that the floor in the room is dry and you are wearing shoes with rubber soles.
To check the health of the windings, you will need a multimeter set to resistance measurement mode (Ohm). If you do not have experience working with electrical appliances, it is better to limit yourself to a visual inspection or invite a specialist. Remember that electric current is invisible and odorless, but can be deadly if handled incorrectly.
Visual inspection and preparation for diagnosis
The first stage is always an external inspection. Often the cause of the breakdown is visible to the naked eye. You will need to remove the back panel of the refrigerator to access the compressor compartment. In some models, such as Bosch or Siemens, access may be limited by plastic covers that require careful dismantling.
Pay attention to the condition of the wires leading to the compressor. If you see melted insulation, blackened contacts, or burn marks on the relay itself, this is a sure sign of a problem. Often the starting relay, which fits directly onto the compressor terminals, has cracks in the housing. Inside such a relay there is a coil and a movable core, which over time can coke or burn.
☑️ Preparation for testing
If no visual defects are detected, it is necessary to remove the starting relay. It is usually mounted on a bracket or simply slipped onto the three pins of the compressor. Carefully remove the relay, being careful not to damage the wires. After removal, inspect the internal contacts of the relay: if black carbon or oxidation is visible on them, most likely the problem is in this unit, and checking the compressor directly may not even be necessary.
Now you need to determine which wire is responsible for what. The compressor terminals often have markings: R (Running - working), S (Starting - starting), C (Common - common). If there are no markings, you will have to check the windings with a multimeter. The resistance between the common and working contacts is usually less than between the common and starting contacts.
Diagnostics of windings with a multimeter
Before applying voltage directly, you need to make sure the integrity of the motor windings. This will eliminate the possibility of a short circuit inside the motor, which, if connected directly, can lead to knocked out plugs or damage to the wiring in the apartment.
Take a multimeter and set it to resistance measurement mode (limit 2 kOhm). Touch the probes to the pairs of contacts on the compressor. You need to get three values: between general and working, between general and triggering, and between working and triggering. The sum of the first two measurements should be equal to the third.
Normal resistance values depend on the engine power, but usually they are within the following limits:
| Pair of contacts | Expected resistance | What does deviation mean |
|---|---|---|
| General - Working | 10 - 30 Ohm | Open or inter-turn short circuit |
| Common - Starting | 20 - 50 Ohms | Starting fault windings |
| Case - Any contact | Infinity (∞) | Breakdown to the case (dangerous!) |
If the multimeter shows infinity (one in the most significant digit) when testing the windings, it means that chain break. A compressor with a broken winding cannot be repaired and requires replacement. If the resistance is close to zero, this indicates a short circuit of the turns.
Methods of direct start of the compressor
If the windings are intact, you can proceed to the most important stage - trying to start the motor bypassing the standard relay. There are two main methods: using a button (or short circuit) and using a capacitor. The first method is more common for quick diagnostics.
The essence of the method is to constantly supply 220V voltage to the general and working contacts, and to the starting contact for a short time, only at the moment of start. To do this, you can use a power cord with a plug, stripping the ends of the wires. One wire is connected to the common contact, the second to the working one. The third wire (from the starting winding) needs to be briefly touched by any of the connected wires.
Connection diagram for starting:1. Phase (L) -> Common contact (C)
2. Zero (N) -> Working contact (R)
3. Short-term: Zero (N) -> Start contact (S)
It is important to make the connection quickly and confidently. As soon as you apply power to the working winding and briefly “kick” the starting winding, the motor should begin to operate with a characteristic hum. If the start-up was successful, the compressor will work until you turn off the power or the thermal relay trips (if it was not removed along with the start-up relay).
Analysis of results and possible malfunctions
After attempting to start, it is necessary to analyze the behavior of the compressor. There are several possible scenarios, each of which indicates a specific problem. Correct interpretation of the results will help you make a decision about repairing or replacing the unit.
If the motor starts, runs smoothly and does not make any extraneous knocks, then the engine itself is working. The problem most likely was with the start relay, which was not energizing the start winding. In this case, it is enough to buy a new relay corresponding to the power of your compressor (the marking is usually indicated on the relay body, for example, RKT, PTC).
If the compressor hums, but does not start even when voltage is directly applied to the starting winding, the following options are possible:
- 🔨 Jamming of the mechanical part: The piston group is stuck due to oil production or foreign objects particles.
- 🔥 Interturn short circuit: The windings heat up, the current increases, but the magnetic field is not enough to start.
- 📉 Loss of compression: The motor rotates, but does not build up pressure (check required pressure gauge).
⚠️ Attention: If the compressor makes a loud metallic knock or clanging sound when starting, immediately turn off the power. This is a sign of destruction of the internal suspension or valve group. Further operation of such a unit is impossible.
It is also worth considering that some modern inverter compressors (found in models Samsung, LG with Linear Compressor technology) cannot be tested using this method. They are controlled by special electronic units that supply a current of a certain frequency. A direct supply of 220V 50Hz to such a motor is guaranteed to output. it is out of order.
Frequently asked questions (FAQ)
Is it possible to leave the refrigerator working with a button instead of a relay?
No, this is a temporary measure only for diagnostics. The starting winding is not designed for long-term operation and will burn out in a few minutes. In addition, without thermal protection, the compressor can. overheat and fail.
Why does the compressor start, but after 10-20 seconds it turns off?
Most likely, the thermal overheating protection relay is triggered. This may be due to the fact that the motor is running without a standard cooling system or the starting winding remains connected in the circuit. The reason may also be low voltage in the circuit. network.
How to determine the power of a compressor for selecting a relay?
The power is indicated on the sticker on the compressor body (in Watts or Horse Power - HP). The power can also be indirectly determined by the current consumed during operation, but the easiest way is to remove the old relay and look at its markings.
Is it dangerous to check a compressor in a living room?
Yes, it can be dangerous. Firstly, there is a risk of electric shock. Secondly, if there is a freon leak in the system, a chemical reaction may occur during the operation of sparking contacts with the formation of toxic gases.