The situation when the refrigerator stops cooling, and the cause of the malfunction turns out to be compressor, often confronts the owner with a choice: an expensive replacement of the unit or an attempt at resuscitation. One of the common diagnoses is an interturn short circuit or open circuit in the starting winding of the motor stator. In normal mode, it is this winding that creates the initial torque necessary to move the piston group from its place. Without it, the rotor only hums, but does not rotate.
However, there is a technically sound way to make the unit work using only working winding. To do this, it is necessary to artificially create a phase shift, which under normal conditions is provided by the starting coil. This can be realized using external capacitor corresponding capacity. This method allows you to extend the life of the compressor, although it requires strict adherence to electrical safety rules and precise selection of elements.
Before starting repairs, you need to understand that starting an engine with one winding is an emergency mode. It does not restore the original characteristics refrigeration unit, but only allows it to function in a gentle mode. The success of the operation directly depends on the condition of the mechanical part: if the pistons are not jammed and the valves are intact, then the probability of a successful start is high. Otherwise, any electrical manipulations will be useless.
⚠️ Attention: All work on connecting the compressor is carried out under a high voltage of 220 Volts. Before attempting to open the cover or disconnect any wires, ensure that the power cord is completely unplugged from the outlet. The residual charge in capacitors can be life-threatening.
Diagnostics of the condition of the windings with a multimeter
The first step is to accurately determine the nature of the fault. The humming of a compressor does not always mean that the starting winding is burning out; sometimes the problem lies in a stuck start relay or a breakdown in the housing. To check, you will need a multimeter switched to resistance measurement mode (Ohm). It is necessary to remove the protective casing from the back of the unit and gain access to the motor contacts.
The contact terminal usually has three contacts: two upper and one lower (or arranged in a triangle). The lowest point is general conclusion (Common). There should be the least resistance between it and one of the upper contacts - this is the working winding. Between the common terminal and the remaining contact, the resistance should be 1.5–2 times higher - this is the starting winding. If the device shows infinity (open circuit) or zero (short circuit) on the trigger coil, the diagnosis is confirmed.
It is also critical to check that there is no breakdown on the housing. One multimeter probe is applied to any contact, and the second is applied to a copper tube or unpainted part of the case. The device should show infinity. If there is at least some resistance, the operation of such a compressor is prohibited, as this threatens an electric shock when touching the metal parts of the refrigerator.
The principle of operation and the role of the capacitor
The asynchronous motor installed in most household refrigerators requires two phases to create a rotating magnetic field. Since there is only one phase in a household network, a second phase is artificially created by including a capacitor in the starting winding circuit. The current passing through capacitive elementis shifted in phase relative to the voltage, which creates the necessary impulse to start the rotor.
When the starting winding burns out, the circuit breaks and the magnetic field becomes pulsating rather than rotating. The rotor cannot start moving on its own. Connecting a capacitor in parallel with the working winding (or in series with the rest of the circuit, depending on the circuit) allows you to simulate the operation of the second coil. In this case, we use a working capacitor, which remains in the circuit constantly, in contrast to the starting one, which is turned off by a relay.
The capacitance of the capacitor plays a key role. If it is too small, there will not be enough torque to start under freon load. If too large, the motor will overheat and the current in the windings will exceed the rated values. For most household compressors with a power of 100–200 W, a value in the range of 25–50 μF is considered optimal. The exact calculation depends on the power of the specific motor.
Necessary tools and materials
To carry out successful resuscitation of the compressor, it is necessary to prepare not only the capacitor itself, but also a number of auxiliary tools. The quality of the wire connections and the reliability of the insulation directly affect the fire safety and durability of the repair. You should not use hastily twisted wires, as vibrations during operation of the unit will quickly destroy the contact.
You will need a set of tools for stripping wires and installation. It is also important to have electrical tape or heat shrink of the appropriate diameter on hand. To connect the capacitor, it is better to use terminal blocks or special lugs that will ensure tight contact with the terminals of the windings.
Below is a list of necessary equipment:
- 🔧 Multimeter for checking resistance and circuit integrity.
- 🧰 A set of screwdrivers and side cutters for dismantling the casing and stripping the wires.
- 🔌 Starting capacitor (capacity 25-50 μF, voltage >350V).
- 🧵 Copper wire with a cross-section of at least 0.75 mm² for extending contacts.
- 🛡️ Dielectric gloves and high quality insulating tape.
⚠️ Attention: It is strictly forbidden to use capacitors of unknown origin or with swollen housings. A faulty capacitor can explode, splashing electrolyte, or cause a short circuit, which will lead to the final failure of the compressor.
Connection diagram and step-by-step instructions
The starting process begins with dismantling the standard starting relay. It will no longer be needed, since its function - short-term supply of voltage to the starting winding - will not be implemented in this circuit. We need to ensure direct connection of the working winding to the network and sequential connection of the capacitor to the second circuit.
Having determined the terminals of the working winding (the least resistance between the common and working contacts), we connect them directly to the 220V network. One wire of the network goes to the common contact, the second to the working one. The capacitor is connected in the gap between the working contact and the free contact (formerly the starting one), or in parallel with the working winding, creating a phase shift. In a simplified circuit for starting with one winding, the capacitor is often placed parallel to the working winding, using the remaining contact as an auxiliary one.
☑️ Compressor connection algorithm
It is important to correctly navigate the conclusions. If the contacts are mixed up, the compressor may hum but not start, or the shaft will rotate in the opposite direction (which is critical for a piston refrigerator compressor and can lead to valve failure). The direction of rotation is usually indicated on the housing or determined experimentally when turned on for a short time.
The table below shows typical resistance values for compressors of various capacities, which will help you identify the windings:
| Compressor type | Operating winding resistance (Ohm) | Starting winding resistance (Ohm) | Total resistance (Ohm) |
|---|---|---|---|
| Low power (up to 100 W) | 15 – 25 | 30 – 45 | 45 – 70 |
| Medium power (100-150 W) | 10 – 18 | 20 – 35 | 30 – 53 |
| High power (>150 W) | 5 – 12 | 15 – 25 | 20 – 37 |
| Industrial units | 1 – 5 | 5 – 10 | 6 – 15 |
What to do if the shaft rotates in the opposite direction?
If after starting you hear an unusual noise or the compressor does not pump, it may be rotating counterclockwise. In this case, it is necessary to swap the wires going from the capacitor to the terminals of the windings.
Checking performance and starting
After assembling the circuit, it is necessary to conduct an initial test. Do not completely solder the connections until you are sure that the system is working. Use clamps or temporarily twisted and insulated contacts for initial switching. When voltage is applied, carefully monitor the behavior of the motor.
A confident start for 1-3 seconds, followed by a smooth hum, is considered normal. If the compressor hums, but does not start, and a characteristic low-frequency hum is heard, it means there is not enough starting torque. In this case, you can try to increase the capacitance of the capacitor by adding a second one in parallel with the first. However, increasing capacity leads to an increase in current and overheating, so you cannot experiment for a long time.
Be sure to check the temperature of the compressor housing after 10-15 minutes of operation. It should be warm, but not hot. If the hand does not tolerate touch for more than 5 seconds, it means that the capacitor capacitance has been selected incorrectly or there is mechanical resistance in the piston group. It is also worth checking the current consumption with current clamps: it should not exceed the rated current indicated on the nameplate.
Safety measures and limitations of the method
Using a compressor with a burnt-out starting winding and capacitor starting is a temporary solution. Operating life such a unit is reduced, as the engine efficiency decreases and thermal loads increase. It is recommended to use such a refrigerator with caution, not overloading it with food and monitoring the temperature inside the chambers.
One of the main problems is the lack of standard thermal protection, which is often built into the starting relay or attached to the case. When operating through a capacitor, the currents may be unbalanced, which will lead to overheating of the windings. It is strongly recommended to install a separate thermal relay or circuit breaker set to a current slightly higher than the operating current to protect the motor from combustion.
It should also be borne in mind that this method is only applicable to asynchronous motors. If your refrigerator has an inverter compressor (often found in models from LG, Samsung, and Bosch in recent years), these instructions do not apply. Inverter motors are controlled by complex electronics and do not have classic starting windings in the traditional sense.
⚠️ Attention: If, after starting, the compressor runs for more than 20 minutes and the housing becomes very hot, immediately disconnect the device from the network. Continued operation will lead to melting of the winding insulation and complete failure of the unit without the possibility of recovery.
Frequently asked questions (FAQ)
Is it possible to start a compressor without a capacitor at all, simply by unwinding the shaft?
Theoretically, if you manually rotate the shaft, a motor with one working winding can continue to operate. However, this cannot be done in a hermetically sealed refrigerator compressor without compromising the integrity of the housing. In addition, the torque of the working winding is not enough to overcome the freon pressure in the system, so this method is unworkable in practice.
Which capacitor is better to use: starting or working capacitor?
For a circuit where the capacitor remains connected to the circuit constantly, it is necessary to use working capacitor (for example, CBB60, CBB61 series). Starting capacitors (usually black in a plastic case) are not designed for long-term operation under voltage and can explode after a few minutes or hours of operation.
Will the cooling capacity of the refrigerator decrease after such a repair?
Yes, the efficiency of the compressor will decrease somewhat. The engine will operate with less efficiency, and it may take longer to operate to reach the set temperature. Noise and vibration levels may also increase. However, for an old refrigerator, this is often the only way to delay the purchase of new equipment.
Why does the compressor hum, but does not start even with a capacitor?
There may be several reasons: insufficient capacitance of the capacitor, an interturn short circuit in the working winding (then the motor cannot be saved) or, most likely, a mechanical wedge of the piston group. If the shaft does not rotate mechanically, electrical methods will not help.
Is it safe to leave such a refrigerator turned on unattended?
Leaving a restored compressor unattended for a long time (for example, when leaving home) is risky. Possible power surges or overheating may result in a fire hazard. It is recommended to use such a unit only under periodic monitoring or install a special socket with overload protection.