A sudden stop of the refrigerator is always stressful for the owner, because food supplies are at risk. Often the cause of a breakdown is the failure of the starting relay, but in some situations it is necessary to exclude or confirm the malfunction of the relay itself. Checking the motor, bypassing the standard starting circuit, allows you to accurately determine whether the “heart” of the unit is alive or the problem lies deeper. compressor. Checking the motor, bypassing the standard starting circuit, allows you to accurately determine whether the “heart” of the unit is alive or the problem lies deeper.
This procedure requires caution and basic knowledge in electrical engineering, since the work is carried out with high voltage. Before you begin diagnostics, you must completely turn off the power to the refrigerator and prepare the necessary tools. Ignoring safety rules can lead to electric shock or permanent equipment breakdown.
In this article we will analyze in detail the algorithm of actions that will help you understand the condition of the engine without using a standard relay. You will learn how to visually evaluate the assembly, how to properly connect the wires for direct starting, and how to interpret the readings multimeter. This knowledge will save time on troubleshooting and will help you make the right decision on repairs.
Visual assessment and preparation for diagnostics
The first stage is always an external inspection, which often allows you to identify obvious defects without the use of complex equipment. The compressor must be dry, without traces of oil, since leakage of freon and oil often indicates depressurization of the housing. If you notice oil stains around the tubes or on the motor housing itself, further checking may be pointless - such a unit requires replacement.
Carefully inspect the electrical contacts on the compressor block. They must be clean, without traces of soot, oxidation or melting of the plastic. Blackened contacts indicate that arcing has occurred in the circuit, which could damage the windings. Also check the integrity of the insulation of suitable wires - cracks or damage to the insulation are unacceptable when working with high voltage.
- 🔌 Unplug the refrigerator and move it away from the wall to access the rear panel.
- 🔧 Remove the protective cover at the bottom of the unit to gain access to the compressor.
- 👀 Visually check the absence of swelling, rust and oil smudges on the engine housing.
- 🧹 Clean the motor surface from dust and dirt with a dry rag before starting measurements.
⚠️ Attention: If traces of severe corrosion or mechanical damage are visible on the compressor housing dents, the risk of current breakdown to the body is extremely high. In this case, carrying out the test under voltage is strictly prohibited.
After a visual inspection, it is necessary to dismantle the starting relay and the protective capacitor, if any. They are usually mounted on the side or top of the compressor and secured with a bracket or plastic housing. Carefully remove these elements to free the winding contacts for connecting measuring instruments.
Necessary tools and safety measures
For high-quality diagnostics, you will need a minimum set of tools that most home craftsmen can find. The main device will be multimetercapable of measuring resistance in a wide range. You will also need a screwdriver to remove the terminals, pliers and possibly electrical tape to temporarily isolate the connections.
Safety is the number one priority when working with household appliances. Make sure the floor under your feet is dry and your hands are not wet. When applying voltage to the windings for a test run, use only good wires with intact insulation. Any careless movement can lead to a short circuit.
It is strictly forbidden to cut through, resolder, or in any way damage the copper tubes coming out of the case. This will not only lead to a gas leak, but can also cause the oil to ignite when in contact with an open flame or spark.
- 📏 Digital multimeter with continuity and resistance measurement function.
- 🪛 Set of screwdrivers (phillips and flat) for removing the protection.
- 🧤 Dielectric gloves to protect hands when working under voltage.
- 💡 Test lamp or socket with an incandescent lamp for checking the circuit (optional).
If you use homemade probes or wires for direct connection, make sure that their cross-section matches the current consumption of the compressor. Thin wires can melt instantly, causing a short circuit. It is best to use wires with a cross-section of at least 0.75 mm².
Checking the integrity of the windings with a multimeter
The most reliable method of primary diagnosis is measuring the resistance of the windings. The compressor terminal block usually has three contacts: two for the working and starting windings and one common. Their location may differ depending on the model refrigerator, so it is important to identify them correctly.
Set the multimeter in resistance measurement mode (Ohms) to the 2 kOhm limit. Touch the probes to different pairs of contacts. You should get three resistance values. The sum of the resistances between two pairs of contacts should be equal to the resistance of the third pair. This is the basic law of physics for connecting windings in series.
⚠️ Attention: If the multimeter shows one (infinity) when testing any contacts, this means a winding break. Repair in this case is impossible, the compressor needs to be replaced.
Normal resistance values depend on the motor power, but are usually within the following limits: the resistance between the working and starting windings is about 30 Ohms, between the working and general windings - 15 Ohms, between the starting and general windings - 10-12 Ohms. The exact numbers may vary, but the ratio should be maintained.
Table of typical resistances
For low-power compressors (up to 100 W), the resistance of the operating winding is 20-35 Ohms, the starting winding is 15-25 Ohms. For high-power models, the values may be lower because thicker wire is used. The main rule: the resistance of the starting winding is always higher than the working one.
It is also necessary to check that there is no breakdown on the housing. Switch the multimeter to diode test mode or to the maximum resistance limit. Touch any contact of the block with one probe, and touch the metal part of the compressor housing with the other (pre-clean off a small spot of paint for better contact). The device should show infinity. If there is resistance or a squeak is heard, the winding is shorted to the housing, operation is dangerous.
Table of typical resistance values
For ease of comparison of the data obtained, we present a table with approximate values for different types of compressors. Remember that these data are for reference only, and small deviations are acceptable.
| Winding type | Resistance (Ohm) | Permissible error | Failure sign |
|---|---|---|---|
| Operating (main) | 10 - 25 | ± 5 Ohm | Open or short circuit |
| Starting | 20 - 40 | ± 5 Ohm | Open or short circuit |
| General contact | Amount Rwork + Rstart | ± 10% | Scheme violation |
| Case (breakdown) | ∞ (Infinity) | 0 | Any value |
If your measurements differ radically from the tabulated data, this is a reason to think about the state of the wire insulation inside the engine. An interturn short circuit is an insidious defect that does not always give a complete break, but changes the resistance and leads to overheating.
With an interturn short circuit, the winding resistance will be significantly lower than normal. Such a compressor can hum, get very hot and knock out the circuit breaker after a few minutes of operation. In the long term, such a motor will still fail.
Direct engine starting method
If checking with a multimeter does not reveal breaks or breakdowns, you can try to start the motor directly, bypassing the relay. This method allows you to check the mechanical part and ability of the rotor to rotate. To do this, you will need to apply 220V voltage directly to the winding contacts.
The connection diagram is simple: one wire from the plug is connected to a common contact, the second wire is supplied to the starting winding through a button (or simply by briefly touching it), and then switches to the working one. However, there is a safer way using a starting capacitor, if it is provided for in the design.
☑️ Safely starting the motor
At the moment of applying voltage to the starting winding winding, the rotor should jerk and begin to rotate. If the motor hums but does not turn, the bearings or piston group may be jammed. If a quiet hum is heard and after a few seconds the plugs are knocked out, there is a short circuit of the turns, which the tester did not detect.
Important: do not keep the voltage on the starting winding for more than 2-3 seconds. This winding is designed for short-term operation only. Prolonged supply of current will lead to its instantaneous combustion. After starting, the motor must operate stably on the working winding.
⚠️ Attention: When connected directly, the compressor does not have overheating protection. Monitor the case temperature with your hand. If it becomes too hot within 1-2 minutes, turn off the power immediately.
Successful starting and smooth operation of the engine for 5-10 minutes indicates that the motor itself is working properly. In this case, the reason the refrigerator is not working lies precisely in the start relay, thermostat or wiring. A faulty relay must be replaced with a similar one.
Diagnostics of mechanical faults
Electrical serviceability of the windings does not guarantee full operation of the unit. Mechanical problems often manifest themselves in the form of unusual noises, knocking or complete jamming. If the motor hums, jerks, but the shaft does not turn, the piston group may be jammed.
Sometimes the so-called “wedging” helps. To do this, increased voltage or a short-term current pulse is applied to the contacts in order to tear the jammed parts out of place. However, this method is risky and requires special equipment, so at home it is better to limit yourself to diagnostics.
- 🔊 A loud metallic knock during operation indicates destruction of the crankshaft liners.
- 📉 Lack of outlet pressure (checked with a finger on the tube) indicates wear of the rings or valves.
- 🌡️ Excessive heating of the housing during normal operation may indicate friction of parts.
If the compressor operates but does not create the necessary pressure for freon circulation, its efficiency is close to zero. You can check the compression by disconnecting the discharge tube and turning on the engine. There should be a powerful flow of air coming from the tube, which can be felt at a distance of 10-15 cm.
Weak compression can also be caused by a malfunction of the valve plate. In this case, the gas is simply distilled from one side of the piston to the other without creating pressure in the system. Repairing such a malfunction at home is practically impossible due to the need for hermetically sealed soldering and vacuuming.
Analysis of results and decision making
After all measurements and test runs, it is necessary to systematize the data obtained. If the windings are intact, there is no breakdown in the housing, and the motor starts directly, feel free to change the starting relay. This is an inexpensive part, and its replacement often brings the refrigerator back to life.
If a break, interturn short circuit or breakdown in the housing is detected, the compressor must be disposed of. Attempts to rewind the engine at home are impractical due to the high cost of the work and the complexity of sealing. The only way out is to install a new compressor or buy a new refrigerator.
Do not forget about the age of the equipment. If the refrigerator is more than 15 years old and its compressor has burned out, it is often more economical to purchase a new unit. Older models consume more electricity, and searching for original spare parts can take a long time.
The final decision on repair or replacement is made based on a comprehensive assessment of the condition of the equipment. Motor diagnostics without a relay is a powerful tool that allows you to avoid unnecessary expenses on calling a technician to simply replace the relay or, conversely, not buying a new part when the motor itself is dead.
Frequently asked questions (FAQ)
Is it possible to check a compressor without a multimeter?
Accurately determine the resistance windings without a device are not possible. However, you can use a 220V incandescent lamp connected in series with the winding. If the lamp is on at full intensity, there is a short circuit; if it is dim, the winding is intact; if it is not on, there is a break. But this method is less accurate and more dangerous.
Why does the compressor hum but does not start without a relay?
Most likely, the piston group or crankshaft bearings are jammed. Also, the cause may be a strong interturn short circuit, due to which the engine does not have enough power to start. In rare cases, the problem is the lack of starting torque, which the second winding normally provides.
Is it dangerous to keep the compressor turned on without a relay for a long time?
Yes, it is dangerous. Without a protection relay and a starting device, the motor may operate in suboptimal mode, overheat and quickly fail. In addition, there is no protection against overcurrent, which can lead to a fire in the wiring if a malfunction occurs.
How to distinguish the working winding from the starting winding?
The working winding always has less resistance, since it is wound with a thicker wire. The starting winding has a higher resistance and is made of thinner wire. By measuring the resistance between the contacts, you can easily identify them by this characteristic.