When the refrigeration unit stops freezing and it becomes warm inside the chamber, the first thing the owner begins to look for is the cause of the breakdown. Often the culprit of the failure is compressor, which simply does not start or works intermittently. Checking the refrigerator motor directly is an effective diagnostic method that allows you to exclude damage to the start relay or thermostat and ensure that the electric motor itself is in good working order.
However, before taking active steps, you need to understand that you are dealing with high voltage electric current and compressed freon gas. Incorrect manipulations can lead to electric shock or failure of the entire system. In this article, we will analyze in detail the device single-phase asynchronous motorused in household appliances, and describe a step-by-step algorithm for safe testing.
To carry out high-quality diagnostics, you will need a minimum set of tools: a multimeter (tester), a set of screwdrivers, pliers and, possibly, a working starting relay for control launch. If you do not have experience working with electrical appliances, it is better to entrust this task to professionals, since the risk of errors when working with high voltage high voltage
Operating principle and design of the compressor
The heart of any refrigerator is a sealed unit, inside which contains piston compressor and an electric motor. Unlike industrial installations, in household models the motor and compressor part are located in a common metal casing filled with inert gas or oil. The electrical part is represented by a stator with windings and a rotor, which rotates inside the stator.
The key feature of such engines is the presence of two windings: working and starting. The working winding provides the main rotation, and the starting winding is needed only at the moment of start to create torque. The starting relay is responsible for switching between them, which often fails before the motor itself. Understanding this diagram is necessary for correct diagnosis.
⚠️ Attention: The inside of the compressor is under high pressure. It is strictly forbidden to open the sealed casing or attempt to drill into it. All work is carried out only on the external electrical part.
The winding contacts are connected to a special block located on the unit body. The start-protection relay is connected to this block. Depending on the model of the refrigerator, be it Indesit, Atlant or LG, the contact arrangement may differ slightly, but the principle of operation remains the same for all asynchronous motors of this type.
Necessary tools and safety measures
Before you start checking the refrigerator motor directly, you need to prepare the workplace and tools. The main diagnostic device will be multimeterwhich will allow you to measure the resistance of the windings and check for a breakdown on the housing. Without this device, it will not be possible to “ring” the circuit qualitatively, since a visual inspection often does not reveal internal breaks.
Safety is priority number one. Working with electrical wiring requires disconnecting the device from the network. You should not rely solely on a switched outlet; it is better to completely cut off the power to the room or use an extension cord with a switch that can be controlled. It is also worth taking care of the dry surface on which the repair will be carried out.
☑️ Preparation for diagnostics
To check, you may also need pliers for removing terminals and insulating tape for temporary insulation of contacts. If you plan to start the motor using a capacitor or direct connection, make sure your hands are dry and the insulation of the tool is intact. Any spark paired with oil can be dangerous.
Dismantling and visual inspection of the unit
To gain access to the electrical part, you need to move the refrigerator away from the wall and remove the back metal cover. It is usually attached to several self-tapping screws, which can be easily unscrewed with a Phillips screwdriver. In some models, for example, old ZIL or Biryusa, access may be limited by the design of the case, but the principle remains the same.
After removing the cover you will see a black "tank" - this is what it is compressor At its end or side there is a plastic box that covers the contact group and the starting relay. Carefully remove the retaining clip or screws to remove this unit. Before doing this, be sure to photograph the location of the wires so that you don’t confuse anything later.
- 🔍 Inspect the wires for the presence of melted insulation or traces of burning.
- 🔍 Check the contact group for oxidation or blackening of the contacts.
- 🔍 Make sure that the starting relay is not cracked and foreign odor.
- 🔍 Check the integrity of the thermal fuse, if it is installed in the circuit.
Often the cause of failure is not the motor itself, but a burnt-out thermal relay or oxidized contacts. If there are visually no signs of a short circuit on the wires and connectors, you can proceed to deeper diagnostics using measuring instruments. Clean contacts are the key to proper operation of the entire system.
Diagnostics of windings with a multimeter
The most reliable way to check the condition of the motor is to measure the resistance of the windings. To do this, switch the multimeter to resistance measurement mode (Ohm). There are usually three pins on a terminal block. You need to “ring” them in pairs. Between the working and starting terminals, the resistance should be the sum of the resistances of each winding relative to the common wire.
Normal resistance values depend on the power of the motor, but usually range from 10 to 30 Ohms for the working winding and from 30 to 50 Ohms for the starting winding. If the device shows infinity (open) or zero (short circuit), then the engine is most likely faulty. It is also important to check that there is no short circuit to the body.
Table of normal resistance values
For different models of refrigerators, the values may differ. Typically the working winding has less resistance than the starting winding. The difference in readings must be significant. If the resistances are equal or close, this is a sign of an interturn short circuit.
When checking for breakdown, one multimeter probe is applied to any contact of the block, and the second is applied to a cleaned place on the compressor housing (for example, to a copper tube, having previously cleaned the paint). The device should show infinity. Any other value indicates that the winding is broken into the housing, and operating such a unit is deadly.
Checking the starting relay and thermostat
Before connecting the motor directly, it is worth ruling out a malfunction of the starting relay. This device is responsible for briefly supplying voltage to the starting winding. In relays with a posistor, the ceramic element itself often breaks, and in induction relays the contacts stick or the coil burns out. You can check the relay by applying voltage to it outside the refrigerator, being careful.
The temperature regulator also plays an important role. If it is faulty and open, the motor power circuit will not close and the refrigerator will not turn on. To check it, you can temporarily short-circuit the thermostat contacts with a wire. If after this the motor starts working, then the problem was in the temperature sensor, and not in the engine.
Sometimes the problem lies in the protective thermal relay, which is located on the compressor housing. It opens the circuit when overheated. If it is “stuck” in the open state, the motor will not receive power. You can check its integrity by the usual ringing: in a cold state, the contacts should ring briefly.
Direct motor connection diagram
If all the elements are in working order, but the motor does not start, you can try to start it directly, bypassing the standard starting relay. To do this, you will need to apply 220 volts to the working winding, and briefly power the starting winding through a capacitor or button. This will allow you to understand whether the engine is capable of developing torque.
The connection diagram is simple: phase and zero are connected to the ends of the working winding. The starting winding is connected in parallel with the working winding, but only at the moment of start (1-2 seconds). It is important not to keep the starting winding energized, otherwise it will burn out. For convenience, you can use a button with normally open contacts.
| Winding type | Wire color (approximate) | Resistance (Ohm) | Function |
|---|---|---|---|
| Working | Red / White | 10-30 | Main rotation |
| Startup | Green / Blue | 30-50 | Start rotor |
| General | Black / Yellow | - | Common zero |
| Ground | Yellow-green | Infinity | Safety |
Upon successful startup, the motor should run smoothly, without buzzing or vibration. If you hear a hum, but the shaft does not rotate, the piston group may be jammed. In this case, sometimes “wedging” by applying increased voltage helps, but this procedure should only be performed by an experienced technician.
Typical faults and methods for eliminating them
One of the common problems is an interturn short circuit in the windings. In this case, the engine may hum, become very hot and knock out the circuit breaker. This can only be checked for sure using an inductance measuring device, but an indirect sign is black smoke and a burning smell when trying to start.
Compressor jamming is another common problem, especially with older units. The oil thickens or burns out, and the piston cannot make its first stroke. Sometimes gently warming up the lower part of the compressor with a hairdryer or hitting a wooden gasket with a hammer helps, but this is a temporary measure.
⚠️ Attention: If after direct starting the motor runs but does not create pressure (does not pump freon), then a mechanical breakdown has occurred inside the compressor (broken connecting rod, worn valves). Repair in this case is impractical; replacement of the unit is required.
It is also worth considering that modern inverter compressors, which are found in models Samsung or LG, cannot be checked using the method described above. They require a special control unit and are not started directly from a 220V network. An attempt to directly connect an inverter motor will lead to its instant combustion.
Frequently asked questions and answers (FAQ)
Is it possible to check the compressor without a multimeter?
Theoretically, you can try to connect it directly to the network, following the start-up diagram, but this is extremely dangerous and does not provide a guarantee accuracy. Without the device, you will not know whether there is a breakdown in the housing, which can lead to an electric shock.
Why does the motor hum but does not start?
This is a sign that the starting winding does not receive an impulse or the shaft is mechanically jammed. It is also possible that there is low voltage in the network or a malfunction of the starting relay, which does not switch the windings.
How many ohms should there be on a working compressor?
The total resistance between the outer contacts should be equal to the sum of the resistances of each winding relative to the middle contact. Typical values: operating 15 Ohms, starting 40 Ohms, total 55 Ohms. Small deviations are allowed.
Is it dangerous to leave a refrigerator with sealed tubes?
Yes, if you are checking the motor on a removed unit, you should not turn it on for a long time without load. The compressor may overheat because the freon circulating through the system also cools the motor. A short run for testing is acceptable.
In conclusion, it is worth noting that diagnosing a refrigerator requires care and accuracy. If you are not confident in your abilities, it is better to call a specialist, since incorrect assembly or connection can lead to a fire or final breakdown of expensive equipment.