The situation when the refrigerator stops cooling, and the compressor only hums or clicks, but does not start, often indicates a malfunction of the start protection relay. This small device is responsible for supplying a starting pulse to the motor winding. In some cases, for example, to carry out urgent diagnostics or check the integrity of the motor, it becomes necessary to start the unit bypassing the standard automation. Direct connection allows you to understand whether the compressor itself is alive, or the problem lies deeper.
However, you should immediately warn: operating refrigeration equipment without standard protection is an emergency measure, not a solution to the problem. Start relay not only supplies current, it also opens the starting winding circuit after gaining speed. Ignoring this step can cause the engine to overheat and burn out in a matter of minutes. Therefore, all the actions described below should be carried out solely for the purpose of short-term diagnostics or as a temporary measure before purchasing a spare part.
Before starting any work on the electrical part of a household appliance, you must strictly observe safety precautions. Working with a mains voltage of 220 Volts poses a real threat to life. When the compressor is directly connected to the network without a relay, the risk of electric shock is maximum, since the contacts often remain open. Make sure that you have sufficient skills in working with power tools and understand the principles of operation of AC electrical circuits.
The principle of operation of the trigger mechanism and the role of the relay
To understand how to bypass the system, you need to know what exactly we are bypassing. A standard single-phase asynchronous motor installed in refrigerator compressorhas two windings: working and starting. The working winding provides the main rotation, and the starting winding is needed only to create the initial torque. Without it, the motor will only hum, remaining motionless.
Standard starting relay (often electromagnetic or posistor) automatically supplies voltage to the starting winding at the moment of start and turns it off when the rotor reaches about 75% of the rated speed. If this element fails, the starting winding circuit remains open and the engine cannot start. Some older models used relays with a thermal release, which also served as overload protection.
When manually starting without a relay, you will have to simulate the operation of this machine yourself. You need to briefly apply current to the starting winding, and then break this circuit, leaving power only on the working one. An error in timing or sequence of actions can lead to the fact that electric motor starts to consume short circuit current, which can lead to knockout of plugs or fire of wiring.
⚠️ Attention: Long-term operation of the compressor without disconnecting the starting winding leads to its instantaneous burnout. It is strictly forbidden to hold the start button pressed for more than 2-3 seconds after the engine starts.
Necessary tools and precautions
To carry out the procedure for “revitalizing” the compressor, you will need a minimum set of tools that most home craftsmen will have. The main requirement is reliability of connections and safety of hands. Do not use damaged wires or tools with damaged insulation.
You will need:
- 🔧 Multimeter —to check the winding resistance and circuit integrity.
- ✂️ Side cutters and pliers —to strip wires and fix contacts.
- 💡 Incandescent lamp (power 100-150 W) - to create a safe load during testing.
- 🧤 Dielectric gloves - a mandatory element of protection when working under voltage.
Before touching the terminals, make sure that the refrigerator is unplugged. Even after being turned off, capacitors can retain a charge, so let the equipment sit for 5-10 minutes. If you plan to use the method with a button, make sure that it can withstand a current of at least 10 Amps, otherwise it will simply burn out at the moment of sparking.
⚠️ Attention: If traces of soot, melted insulation, or a burning smell are visible on the compressor housing or wires, it is prohibited to start the unit. This can lead to a fire.
Diagnostics of the windings before starting
Before applying voltage, you must make sure that the winding itself is electric motor in good condition. Often the cause of failure is not the relay, but an interturn short circuit or a break in the windings. To do this, remove the back cover of the refrigerator, gain access to the compressor and remove the faulty relay along with the starting capacitor (if any).
On the compressor terminal block you will see three contacts. They are usually arranged in a triangle. You need to test them with a multimeter in resistance (Ohm) measurement mode. Find the pair of contacts with the highest resistance - these are the ends of the working and starting windings connected in series. The third contact will be common.
The resistance between the common contact and the contact of the working winding should be the smallest (usually 10-20 Ohms), and between the common and starting windings it should be average (30-50 Ohms). The sum of these two values should equal the resistance between the extreme contacts. If the multimeter shows infinity (open circuit) or zero (short circuit), start such a motor pointless —it requires replacement or rewinding.
Methods of direct start of the compressor
There are several ways to start the motor bypassing standard automation. The simplest and relatively safe method is to use a button with normally open contacts. This method allows you to manually simulate the operation of the start relay. You will need any button (for example, from a doorbell or starter) that can withstand a current of up to 10-15 Amps.
The connection diagram is as follows: the phase wire from the socket is connected to one contact of the button. The second contact of the button is connected to the contact of the starting winding on the compressor. The working winding is connected to the network directly (via a common contact). When the button is pressed, current flows to the starting winding, the motor begins to rotate, and the button must be released immediately.
A more advanced option is to use starting capacitor a suitable capacitance (usually from 10 to 30 μF, voltage of at least 300 V). The capacitor is connected in parallel with the starting winding through a button. This creates a phase shift necessary for a softer and more confident start of the engine, reducing starting currents and the load on the network.
☑️ Check before starting
Step-by-step instructions connection
Let's consider the connection process in more detail. First determine the purpose of the contacts on the compressor block. Depending on the manufacturer (Atlant, Indesit, Bosch), the markings may differ, but the arrangement is often standard: two contacts on top, one on the bottom. The common contact is often located separately or marked with a letter C (Common).
Prepare two wires with stripped ends. Connect one wire to the power plug and the common contact of the compressor. The second wire will go through the button to the start contact. Connect the working contact directly to the second wire of the plug (neutral). Make sure that all twists are securely insulated with electrical tape.
Plug the plug into the outlet. Press the start button. You will hear a hum and, after a split second, the characteristic sound of the engine starting. As soon as the engine picks up speed (this happens within 0.5–1 second), release the button. The motor should continue to run on its own. If after releasing the button it stops, the problem may be in the mechanical part or the wedge.
| Parameter | Normal value | Critical value | Action |
|---|---|---|---|
| Resistance starting winding | 20–50 Ohm | 0 Ohm or ∞ | Replacing the compressor |
| Working winding resistance | 10–25 Ohm | 0 Ohm or ∞ | Replacing the compressor |
| Resistance to housing | ∞ (infinity) | Any value | Stop urgently, breakdown |
| Starting current (approximately) | 10–15 A (short-term) | > 20 A | Check the network and wires |
What to do if the compressor hums, but the shaft does not spin?
If a powerful beep is heard when voltage is applied, but the shaft stands still, the piston group may be jammed. In this case, sometimes the “wedging” method helps by applying increased voltage (through a transformer) or a short-term pulse, but this requires special equipment and is dangerous for the home craftsman. Most often, such a compressor must be replaced.
Risk analysis and temporary operation
Using the refrigerator in the “without relay” mode is possible only as a temporary measure. You must constantly monitor the process: turn on the unit only in your presence, monitor the temperature of the compressor housing and the sound of its operation. The absence of a thermal relay means that if there is an overload or voltage surge, the motor will burn out, since no one will break the circuit.
In addition, without a capacitor (if it is provided for in the design) efficiency the motor drops, and the starting currents increase. This puts extra stress on the wiring in the house. If you notice that the wires of the plug or socket are heating up, operation must be stopped immediately.
It is also worth considering that in modern inverter models (LG Linear, Samsung Digital Inverter) this method is not applicable at all. There, starting and speed control are carried out by complex electronics, and a direct connection to a 220V network will damage the compressor instantly. The described methods are only suitable for classic linear compressors.
Common mistakes during self-repair
One of the most common mistakes is confusion between the starting and operating windings. If you apply full mains voltage to the starting winding (which is designed for short-term operation) and hold it for a long time, it will burn out almost instantly. Always double-check the resistance before connecting.
Another mistake is using too thin wires for a temporary circuit. The inrush current is high and the thin conductor may melt the insulation or cause a fire. Use copper wires with a cross-section of at least 1.5 mm², and preferably 2.5 mm².
Some craftsmen try to replace the relay with a jumper, leaving the starting winding on constantly. This is a serious mistake. The starting winding is not designed for long-term operation under load. After a few minutes of such operation, it will heat up, the insulation will be destroyed, and a short circuit will occur.
⚠️ Attention: Do not leave a refrigerator running unattended, running bypassing the standard protection. The risk of fire in the event of an emergency is extremely high.
Completion of diagnostics and installation of a new relay
If you managed to start the compressor manually and it runs smoothly, picks up speed and cools, then the motor itself is working. The problem really was with the relay. Now your task is to find a replacement. The old relay needs to be removed, its markings must be rewritten (for example, RT-K, P3, 170030060057) and purchased an analogue at a spare parts store.
Installation of a new relay is simple: it is put on the compressor contacts until it clicks and is secured with a bracket or spring clips. It is important to orient the relay correctly (the arrow UP should point up), since there may be a ball or a posistor inside that operates under the influence of gravity or requires a certain position.
After installation, assemble the circuit, plug in the refrigerator and observe. If after 10-15 seconds the humming stops and quiet, uniform operation begins, the repair is completed successfully. If the clicks are repeated, perhaps the wrong power relay has been selected or the problem lies in the compressor itself (for example, weak torque).
Is it possible to use a relay from another refrigerator?
Theoretically, yes, if the current characteristics and type of compressor match. However, it is better to look for an exact analogue by catalog number. A relay with a lower current will burn out, while a relay with a higher current may not open the starting winding in time.
Questions and answers (FAQ)
How long can you safely keep the start button pressed?
The pressing time should be no more than 1-2 seconds. This is enough for the rotor to gain inertia. Holding the button for more than 3 seconds will cause the starting winding to overheat and possibly burn out. If the motor does not start within 2 seconds, release the button, wait 5 minutes and try again.
Is it possible to start a three-phase compressor from a single-phase network without a relay?
Three-phase compressors are rare in domestic refrigerators. If this is exactly what you have, simply supplying 220V to two phases is not enough - the engine will not start or will overheat. He needs a large-capacity phase-shifting capacitor or a frequency converter. The button method is ineffective here.
Why does the compressor start from the button, but immediately knocks out the machine?
This indicates a short circuit in the motor windings or wiring, or that the starting current is too high due to mechanical jamming. Also, the reason may be a malfunction of the wiring itself in the house, which cannot withstand peak loads.
Where to find the markings of a suitable relay?
The markings are usually applied to the body of the relay itself (for example, Danfoss 101L0020) or on a sticker inside the refrigerator compartment, where the technical characteristics of the model are indicated. You can also find the spare part number in the operating instructions.