The situation when the refrigerator stops humming and it gets warmer inside often takes you by surprise, especially if the breakdown happened over the weekend. In most cases, the culprit is the starting relay, which stops sending an impulse to the starting winding of the electric motor. Experienced craftsmen know that for diagnostics or emergency start-up of the unit, you can temporarily exclude this element from the circuit by applying voltage directly.
However, this method is exclusively diagnostic and requires strict adherence to safety precautions, since the work is carried out with high voltage. Direct connection allows us to understand whether the motor itself is alive, or whether the problem lies deeper in the electrical part. It is important to understand that constant operation of the refrigerator, bypassing the standard automation, is impossible and even dangerous.
In this article we will analyze the trigger mechanism in detail, describe the algorithm of actions for temporary starting and explain why you cannot leave the refrigerator in this state for a long time. You will learn how to correctly identify the winding terminals and what tools are needed to carry out the work safely.
⚠️ Attention: All manipulations with the electrical components of the refrigerator should only be carried out when the power is disconnected from the mains. Residual voltage can cause serious damage to health.
The design of the starting mechanism and the role of the relay
In order to understand how to start refrigerator compressor bypassing the standard system, you need to clearly understand what function the starting relay performs. The electric motor of the refrigeration unit is asynchronous and has two main windings: working and starting. The working winding creates the main magnetic field, and the starting winding is needed only at the moment of start to create the initial torque.
The starting relay is an electromagnetic switch that closes the starting winding circuit at the moment the compressor is turned on. Once the motor rotor reaches the required speed (usually about 75% of rated speed), the current in the circuit drops and the relay opens, turning off the starting winding. If this does not happen, the motor may burn out from overheating.
In addition, modern systems often use a thermal protection relay, which opens the circuit when the temperature of the motor housing critically increases or during current surges. Start-protective relay combines both functions. If it malfunctions, the engine either hums, but does not start, or does not make any sounds at all.
- 🔌 Electromagnetic relay - closes the contacts when the starting current passes through the coil.
- 🔥 Thermal protection - opens the circuit when the bimetallic plate overheats.
- ⚙️ Starting winding —provides initial rotor torque.
- 🔄 Working winding —supports engine rotation in normal mode.
Understanding these processes is critically important, since artificially turning on the motor requires simulating the operation of the starting part of the circuit. Without this, the rotor will remain motionless, and the windings will begin to heat up.
Why do relays fail?
A frequent cause of failure is oxidation of contacts or sticking of the core due to aging of materials. The relay can also burn out due to frequent power surges in the network or jamming of the compressor itself when the starting current becomes too high.
Necessary tools and precautions
Before you begin dismantling the relay and connecting the wires, you need to prepare the workplace and tools. You will need a set of screwdrivers with different slots, pliers, insulating tape and, preferably, a multimeter for continuity testing. You may also need a working starting relay or a special starting capacitor for testing if you plan not just to start, but to check the operation of the motor under load.
Safety is priority number one. Make sure the refrigerator is completely unplugged. Do not touch the compressor's metal parts and conductors with wet hands. If you plan to supply voltage for testing, use a grounded socket and, ideally, a residual current device (RCD).
For temporary starting, they often use a button with normally open contacts or simply carefully connect the wires with insulated clamps. Strictly prohibited twist the wires without proper insulation, since at the moment of starting the currents are large and a spark breakdown is possible.
☑️ Preparation for diagnostics
Diagnostics of faulty relays and windings
Before making a decision about starting without a relay, you need to make sure that the problem is in it and not in the compressor itself. A visual inspection often gives the first clues: if a ball is heard knocking inside the relay or traces of burning and soot are visible on the contacts, then the element is faulty. However, external integrity does not guarantee operation.
The most accurate test method is to test the windings with a multimeter. There are usually three terminals located on the compressor housing. It is necessary to determine which of them corresponds to the working winding, which is the starting winding, and which is common. The resistance between the common and working terminals is usually less than between the common and starting terminals.
You should also check the resistance between the compressor housing and any of the terminals. If the multimeter indicates the presence of a circuit (beeps), it means that something has happened, and such a refrigerator should not be operated under any circumstances. This is a direct threat to life. breakdown to the housing, and such a refrigerator should not be used under any circumstances. This is a direct threat to life.
| Check parameter | Normal value | Failure sign |
|---|---|---|
| Working winding resistance | 10-30 Ohm | Infinity (break) or 0 (short circuit) |
| Starting winding resistance | 30-90 Ohm | Significantly higher than normal or break |
| Resistance between the leads and the body | Infinity | Any value (insulation breakdown) |
| Thermal relay integrity | 0 Ohm (closed) | Infinity (open circuit) |
If the diagnostics showed that the windings are intact and the relay does not work, you can proceed to the temporary start procedure. Remember that the purpose of this action is diagnostics or emergency defrosting of food, but not a long-term solution.
Direct connection diagram for the compressor
The process of starting a motor without a standard relay consists of manually applying voltage to the starting winding at the moment of switching on. To do this, you need to get to the contact group on the compressor. Typically, the pins are designated by letters or colors: S (Start) - starting, R (Run) - working, C (Common) - common.
The action diagram is as follows: the power cable (phase) is connected to the common and working terminals and zero). A wire is connected to the starting terminal, the second end of which is briefly shorted to the working or phase wire. At this moment the rotor should start moving. As soon as the engine starts, the wire from the starting terminal must be immediately removed.
For a safer implementation of this process, you can use a button from an old washing machine or any powerful toggle switch. One contact of the button is connected to the phase going to the working terminal, and the second to the starting terminal of the compressor. Pressing the button simulates the operation of a relay.
- 🔌 Determine the common terminal (usually there is one, and the other two are nearby).
- ⚡ Connect zero to the common terminal, and the phase to the working one.
- 🖱️ Organize a temporary short circuit between the phase and starting output.
- 👂 Listen to the characteristic start click and the hum of a running motor.
⚠️ Attention: Keeping the starting winding energized for more than 2-3 seconds after starting the engine is prohibited! This will lead to overheating and burning of the starting winding, since it is not designed for long-term operation.
Using a starting capacitor for starting
A softer and safer way to start than directly shorting the wires is to use a starting capacitor. This method allows you to create the necessary phase shift for the occurrence of torque, similar to how a standard relay does it, but in manual mode or through a button.
The capacitance of the capacitor is selected experimentally or calculated based on the engine power (usually from 4 to 10 μF for household refrigerators). The capacitor is connected to the starting winding circuit in series with the button. When the button is pressed, the capacitor charges and transfers energy to the starting winding, helping the rotor to spin up.
The use of a capacitor reduces starting currents and makes starting smoother, which is especially important for compressors with symptoms wear. However, in this case, the starting winding circuit must open immediately after the engine enters operating mode.
Why you can’t operate a refrigerator without a relay all the time
Many users, having successfully started the motor manually, ask the question: why change the relay if everything works anyway? The answer lies in the physics of how an electric motor operates. The starting winding is made of thinner wire and is not intended for long-term current flow. If you forget to turn it off in time, it will burn out in a matter of minutes.
In addition, the standard relay provides protection against overloads. If the compressor jams or a power surge occurs, the relay will open the circuit, saving the expensive unit from a fire. When working bypassing this protection, any failure in the network or mechanical knocking of the pistons will lead to fatal consequences for the motor.
Also, the lack of automatic shutdown of the starting phase leads to strong heating of the compressor, oil degradation and loss of the refrigerant properties. The service life of the engine in this mode is reduced significantly, and soon the entire unit will need to be replaced.
Frequently asked questions and answers (FAQ)
Is it possible to leave the refrigerator to operate without a relay overnight?
No, this is strictly prohibited. Without a thermal relay and automatic shutdown of the starting winding, there is a high risk of fire or failure of the compressor at any time. Leaving such a refrigerator unattended is dangerous to life and property.
It hums, but does not start - will starting without a relay help?
If, when connected directly (in compliance with all safety measures), the compressor hums, but the rotor does not move even when a pulse is applied to the starting winding, this may indicate a jammed mechanical part (piston group) or interturn closure. In this case, a simple start will not help, the compressor will need to be repaired or replaced.
How to determine which wire to connect where if there is no marking?
You need to use a multimeter in resistance measurement mode. Find the pair of contacts with the least resistance - this is the working winding. The third contact will be the starting contact. The common contact is determined by the exclusion method or by continuity: the resistance between the common and the working plus the resistance between the common and the starting should give the resistance between the working and the starting.
The thermal relay has burned out, is it possible to close it?
Technically, it is possible to close the contacts of the thermal relay, and the motor will start. However, you remove the overheating protection completely. In case of any malfunction (clogged condenser, lack of freon, oil aging), the compressor will overheat and burn out. This is a temporary solution only for testing, but not for operation.
What resource does the compressor have after starting bypassing the relay?
The resource is unpredictable and depends on how quickly you notice overheating or abnormalities in operation. However, the likelihood of failure increases many times over. The standard relay prolongs the life of the motor by cutting off critical operating modes. Without it, you are playing Russian roulette with equipment.