A situation when the refrigerator suddenly stops freezing, and only a quiet hum or hum is heard inside single click, familiar to many owners of household appliances. Often the cause of such a breakdown is the failure of the starting relay, which is responsible for starting the engine. A temporary solution to the problem, which allows you to resuscitate the unit before the technician arrives or a spare part is purchased, is to directly connect compressor bypassing the burnt element. This requires accuracy, understanding of electrical circuits and strict adherence to safety precautions.
However, it is worth understanding that starting single-phase asynchronous motor without a starting winding or special devices is possible only for a short period of time for diagnostics or emergency cooling. Continuous operation in this mode is unacceptable, since the motor does not have overload protection and a mechanism for disconnecting the starting winding. Next, we will analyze in detail how to correctly perform this operation, what tools are required and how not to permanently damage the equipment.
Before starting any manipulations with the electrical part, it is necessary to completely de-energize the refrigerator. Remove the plug from the outlet and make sure there is no voltage on the wires. Even briefly touching live parts under load can lead to serious consequences. Your safety is priority number one, so do not ignore the basic rules of electrical engineering.
The principle of operation of the starting relay and the need to bypass it
The starting relay in household refrigerators performs a critical function: it briefly supplies voltage to the starting winding of the engine, creating the necessary torque to start the rotor. As soon as the engine picks up speed, the relay opens the starting winding circuit, and the motor continues to operate on the main one. If this mechanism breaks down, the engine hums, but cannot start, since the magnetic field is not enough to rotate.
Connecting a motor without a relay involves creating an artificial impulse or using an external button to apply voltage to the starting winding. This simulates the operation of a standard device. It is important to note that starting winding is not intended for long-term operation under load. If you leave voltage on it after starting, it will quickly burn out, which will lead to expensive repairs or replacement of the compressor.
There are two main types of relays that are found in old and new models: posistor and induction. The posistor ones work by heating the element, which increases the resistance, while the induction ones use the current in the main winding to open the contacts. With manual starting, we actually replace the function of closing the contacts, ignoring the automatic opening, which will now have to be controlled manually or using a timer.
⚠️ Attention: Direct connection without controlling the time the starting winding is turned on can lead to instant overheating and failure of the motor. Do not leave the refrigerator running in this way unattended for more than 15-20 minutes.
The purpose of this procedure is most often diagnostic: you need to check whether the compressor itself is alive. If during direct start the motor runs smoothly and picks up speed, then the problem lies precisely in the control circuit or relay. If the hum persists and the shaft does not rotate, the mechanical part may have jammed or the winding has burned out.
Necessary tools and precautions
To carry out work to start the compressor, you will need a minimum set of tools that most home craftsmen can find. The key is a working wiring diagram and understanding the color coding of the wires. You should not rely only on memory, since different manufacturers (Indesit, Atlant, Bosch) may have different colors.
You will need the following tools and materials:
- 🔧 Screwdrivers (Phillips and flathead) for removing protective covers and terminals.
- 🔌 Insulating tape or heat shrink tubes for insulating connections.
- ⚡ Tester (multimeter) to check the integrity of the windings and the absence of a short circuit.
- 🖐️ Dielectric gloves for protection against electric shock.
- 🔦 Flashlight for illuminating the working area in the compressor niche.
Before starting work, inspect the compressor for external damage. If traces of oil, soot, or melted plastic are visible on the terminal box, further operation may be hazardous. Also check the integrity of the wires: they should not be frayed or have exposed areas.
Pay special attention grounding. A refrigerator is a metal case, which can become energized if the insulation breaks down. Make sure that the outlet into which you plan to plug the unit after manipulation has a working ground circuit. Working with electrical appliances in wet rooms (for example, in a kitchen with a wet floor) is strictly prohibited.
⚠️ Attention: Capacitors in some control circuits can retain a charge even after being disconnected from the network. Before touching the contacts, wait a few minutes or carefully discharge them through the dielectric.
Connection diagram and color coding of wires
To correctly connect the motor, you need to understand the leads coming out of the compressor. There are usually three of them (sometimes four if there is additional protection), and they are located on the terminal block in a certain geometry. There may be no standard marking, so you have to rely on the location and color of the wires.
The three main terminals are the common wire, the starting winding wire and the working winding wire. Common wire (Common) is often connected to the phase or neutral of the network directly. The starting winding has more resistance, and the working winding has less. It is this difference that the multimeter uses for identification.
Table of winding resistances
The table shows approximate resistance values. The exact numbers depend on the compressor power. For low-power models, the resistance of the working winding can be about 10-20 Ohms, and the starting winding - 30-50 Ohms. If the device shows infinity - an open circuit, if zero - a short circuit.
For clarity, we provide a table of typical color designations, although you cannot rely on them 100% without checking:
| Output type | Possible wire color | Function | Resistance |
|---|---|---|---|
| Common (C) | Black, White | Network connection | Base contact |
| Working winding (R) | Red, Green | Main work | Low |
| Start winding (S) | Blue, Yellow | Motor start | High |
| Grounding | Yellow-green | Safety | On the body |
The identification process begins with searching for a common wire. Measure the resistance between all pairs of contacts. The pair with the least resistance is the working and starting windings, and the third, remaining contact is the common one. Next, by measuring the resistance between the common wire and the other two, you will determine which winding is which: where the resistance is greater, there is the starting winding.
Step-by-step instructions for starting the compressor
Once the pins have been identified, you can begin assembling the temporary circuit. To do this, you will need a piece of wire with a plug and, preferably, a button without fixation (for example, from a doorbell) or simply an insulated conductor for a short-term circuit.
The algorithm of actions is as follows:
- Connect one wire from the plug (phase or zero) to the common terminal of the compressor.
- Connect the second wire from the plug to the output of the working winding. This will provide power to the main circuit.
- To start, you need to briefly connect the output of the starting winding with the wire going to the working winding (or to the common one, depending on the circuit, most often the starting winding is connected to the working one).
- At the moment of power supply, press the short circuit button to the starting winding. The motor should hum and start.
- As soon as the engine picks up speed (in 1-3 seconds), the button must be released, breaking the starting winding circuit.
If everything is done correctly, the compressor will continue to operate smoothly. If you only hear humming and clicking noises, you may have the windings mixed up or the motor may be faulty. In this case, turn off the power immediately. Repeated startup attempts should be made no earlier than after 5-10 minutes to give the thermal relay time to cool down.
☑️ Check before starting
You will have to monitor the temperature of the compressor housing. If it starts to heat up quickly (becomes hotter than 80-90 degrees), it must be turned off urgently, even if the refrigerator has not yet reached the temperature.
Diagnostics of faults during startup
During the manual startup process, you can identify a number of hidden defects that are not visible during external inspection. For example, if the engine starts but has strong vibration or knocking noises, this may indicate worn bearings or damaged valve trains. In this case, further operation will lead to complete destruction of the compressor.
If the motor hums, but does not start even when a pulse is applied to the starting winding, the following reasons are possible:
- 🔋 Jagging piston group - mechanical damage inside the pressurized unit, often requiring replacement of the unit.
- 🔥 Interturn short circuit —the windings are overheated, the resistance has dropped, the current increases, the protection is triggered.
- 📉 Voltage drop on the network —the old motor may not have enough power to start, try connecting it through a stabilizer.
Another important parameter is current consumption. If you have the opportunity to connect an ammeter to the open circuit, check the operating current. For household refrigerators, it is usually 0.5–1.5 Amperes in operating mode. If the current is significantly higher (more than 2-3 Amperes), it means that the engine is overloaded and its resource has been exhausted.
Temporary solution or final repair?
The use of a direct start circuit without a relay is permissible only as a temporary measure. Operating the refrigerator in this mode for more than a few hours carries risks. Firstly, there is no protection against overheating, which can lead to a fire hazard. Secondly, the compressor operates in a non-optimal mode, which shortens its service life.
If after starting it turns out that the motor itself is working, it is strongly recommended to purchase and install a new starting relay. This is an inexpensive part that will ensure proper operation of the starting winding and engine protection. Replacing the relay takes 10-15 minutes and does not require special equipment other than a screwdriver.
If the compressor does not start even with a kick, or operates with obvious signs of malfunction, it is more economically feasible to replace the entire unit. Repairing the hermetic unit at home is impossible, and replacing the compressor requires evacuation of the system and refilling the refrigerant, which only specialists with the equipment can do.
Is it possible to leave the refrigerator working without a relay all the time?
Theoretically, if you assemble a circuit with a button or timer that will simulate the operation of the relay, this is possible. However, the reliability of such a design will be low. The standard relay is selected by the manufacturer for specific motor parameters. The use of "crutches" is fraught with the failure of an expensive compressor due to untimely shutdown of the starting winding.
Why does the compressor hum, but does not start?
The hum means that electric current enters the windings and creates a magnetic field, but the torque is not enough to turn the rotor. Reasons: jammed mechanics, break in the starting winding, relay malfunction or low voltage in the network. Often, “wedging” by applying increased voltage (by professionals) or replacing the relay helps.
How to determine a burnt-out compressor without disassembling?
Ring the windings with a multimeter. If there is resistance (not infinity) between any terminal and the housing, there is a breakdown to the housing, the compressor is faulty. If the winding resistance is zero, there is a short circuit. If the resistance is infinitely large between all contacts, there is a break. In all these cases, the motor must be replaced.
Is it dangerous to touch the tubes of a running compressor?
Yes. The outlet tube (discharge) can heat up to 80-90 degrees or higher, which will cause a burn. The suction tube, on the other hand, may be very cold and covered with condensation or frost. In addition, if the pressure tubes are damaged, oil may escape or