How to check the refrigerator motor directly without a relay

The situation when the refrigerator stops cooling, but there is silence inside or, conversely, a hum is heard, but there is no cold, often confuses the owner. In most cases, the problem lies in the start-up relay, which stops sending an impulse to start, or in the compressoritself, which could have failed. Before buying a new unit or calling a technician with an expensive tool, it makes sense to conduct an initial diagnosis of the motor. This will allow you to understand whether it is worth repairing the device at all or whether its disposal is the only correct solution.

Checking electric motor directly is an emergency method that gives an instant answer to the question of the viability of the windings and the mechanical part of the piston group. However, it is worth understanding that operating the motor bypassing the standard automation carries certain risks. Without a thermal relay and the starting mechanism, the engine will not be able to operate for a long time and safely, so the purpose of such a procedure is only a short-term start for diagnostics, and not constant operation.

This procedure requires strict adherence to safety precautions, since you will be working with a mains voltage of 220 volts and exposed contacts. Any mistake can lead to electric shock or permanent failure of the equipment. In this material we will analyze a step-by-step algorithm of actions, the necessary tools and criteria for assessing the condition of the unit.

⚠️ Attention: Perform all manipulations with the electrical components of the refrigerator only with the power cord completely disconnected from the network. Connection to the outlet is carried out exclusively at the time of starting verification.

Necessary tools and safety measures

To carry out high-quality diagnostics, you will need a minimum set of tools that most home craftsmen can find. The key device here is multimeter (tester), which allows you to measure the resistance of the windings and check the circuit for breakdown. Without it, “testing” the engine will be impossible, since it is impossible to determine the integrity of the coils by ear or appearance.

You will also need pliers, a screwdriver for removing the compressor casing, and possibly electrical tape. To organize a direct start, they often use a special button with a capacitor or a temporary circuit with a clamp. It is important to ensure good illumination of the working area, since the contacts are located in the lower part of the unit, where light falls poorly.

• 🛠️ Multimeter (necessarily with Ohm resistance measurement mode).
• 🔌 Wires with clips ("crocodiles") for temporary connection.
• 🔧 Set screwdrivers (phillips and flat) for dismantling the protection.
• 🧤 Dielectric gloves for additional insulation of hands.

Particular attention should be paid to the condition of the wire insulation. If you see melted insulation, cracks in the motor housing, or traces of burning, further diagnostics may be dangerous. In such cases, it is better to immediately stop work and evaluate the feasibility of replacing the entire assembly.

Dismantling and preparing the compressor for diagnostics

The first stage of work is access to the electrical part of the engine. The compressor in modern refrigerators is usually located in a niche on the back wall and is covered with a metal or plastic casing. It is necessary to unscrew the fixing screws and remove the cover to gain access to the black cylindrical block.

A starting relay and a thermal relay are attached to the motor pipe. It is this node that we have to temporarily exclude from the chain. The relay is usually fixed on three contacts included in the compressor housing. Carefully remove the plastic relay box by disconnecting it from the motor terminals. Be careful not to pull sharply, so as not to damage the fragile contacts.

After dismantling the relay, you will see three contacts arranged in a triangle. Two of them are located vertically (or horizontally depending on the model), and the third is separate. These are the conclusions of the windings: starting, working and general. They must be cleaned of oxides, if any, to ensure reliable contact with the multimeter probes.

⚠️ Attention: Do not allow moisture to get inside the contact group. Moisture can distort resistance readings or cause a short circuit when voltage is applied.

Checking the integrity of the windings with a multimeter

Before applying voltage, you must make sure that the motor windings are intact and do not have a short circuit. Set the multimeter to resistance measurement mode (usually the limit is 2000 ohms or 2 kohms). If the device shows a unit or an infinity sign when the probes touch any two contacts, this means an open circuit.

Normally, you should get specific numerical values. The resistance between the common contact and the working winding is usually 10-30 Ohms, and between the common and starting windings - 30-50 Ohms. The resistance between the starting and working windings should be the sum of the two previous values. Significant deviations from these standards indicate an interturn short circuit or wire burnout.

The most important step is checking for breakdown to the housing (ground). Press one multimeter probe to any cleaned area on the metal body of the compressor (where there is no paint), and with the second touch each of the three contacts. The device should show infinity (one in the most significant digit). If you see any resistance or hear a squeak, the engine is broken into the housing.

If all measurements are normal, you can proceed to the next stage - trying to start. However, remember that the electrical integrity of the windings does not yet guarantee the serviceability of the mechanical part.

Direct connection diagram for starting the engine

The engine is started directly by applying 220V voltage to the common and working contacts, as well as briefly connecting the starting contact to create torque. Since there is no standard relay, this function will have to be performed manually or using a button. The circuit looks like this: the phase goes to the working contact, the zero goes to the common contact, and the starting contact closes with the working contact for a split second.

To implement this method, it is convenient to use a button with normally open contacts (for example, from a doorbell) or just two wires with clamps. One wire is permanently connected to the network and the working terminal of the motor. The second wire is connected to the network at one end, and with the other end you touch the starting terminal.

As soon as you apply voltage and briefly close the circuit start, the engine should make a characteristic hum and start working. If only a humming sound is heard, but the shaft does not rotate, the piston group may be jammed or there is no starting torque due to weak contact.

⚠️ Attention: The time for applying voltage to the starting winding should not exceed 1-2 seconds. Long-term retention can lead to burnout of the starting winding, since it is not designed for continuous operation.

Analysis of results and typical malfunctions

Successful starting of the engine does not mean that it is fully operational. It is necessary to carefully monitor its operation for 1-2 minutes. The motor should run smoothly, without strong vibration or extraneous knocks. If the compressor starts, but turns off after 10-20 seconds (even without a relay), this may indicate that it does not gain the required speed or overheats instantly. A common problem is the piston group. In this case, the engine hums, consumes huge current (knocks out the circuit breakers), but does not start. Sometimes the “swinging” method helps, when the voltage is applied in short-term pulses, but this is a risky procedure that can finally finish off the unit.

A common problem is jamming piston group. In this case, the engine hums, consumes huge current (knocks out the circuit breakers), but does not start. Sometimes the “swinging” method helps, when voltage is applied in short-term pulses, but this is a risky procedure that can completely kill the unit.

It is also worth paying attention to the color of the gas coming out of the pipes (if it is possible to check) and the smell. The smell of burnt insulation or oil indicates internal problems. If the engine runs but does not create compression (no output pressure is felt), then the valves or piston rings are worn out.

What to do if the engine hums but does not start?

This may be a sign of a wedge or insufficient starting torque. Try to carefully (with a gloved hand!) rotate the motor shaft in different directions with the power off. If the shaft does not turn, the compressor is mechanically jammed. If it turns but does not start, there is probably an interturn short circuit or loss of capacity of the starting winding.

It is important to note that operation without oil (if freon leaks along with oil) is unacceptable. If the refrigerator has been standing for a long time and oil has leaked from the pipes, you cannot run such a motor “dry” - it will burn out in minutes.

Limitations of the method and final conclusions

Checking the refrigerator motor directly is exclusively a diagnostic procedure. It is strictly forbidden to operate the refrigerator without a start relay and thermal protection. The relay provides the necessary phase shift for starting, and thermal protection turns off the motor if it overheats. Without these components, the risk of a fire or complete failure of the compressor increases many times over.

If during the test it turns out that the windings are intact, there is no breakdown in the housing, and the engine starts and runs smoothly, then the problem lies in the starting relay. Replacing it will solve the problem. If the engine does not start, hums or knocks out plugs, the compressor needs to be replaced, since repairing this unit at home is not economically feasible.

• 🔍 The integrity of the windings is the first and main test criterion.
• ⚡ The absence of a breakdown on the housing guarantees safe operation.
• 🔄 A smooth sound of operation indicates the serviceability of the mechanics.
• 🚫 Constant operation without a relay is prohibited by equipment manufacturers.

Always weigh the cost of a new compressor and the work to replace it (including refilling with freon) with the cost of a new refrigerator. Often, repairing an old unit can cost 70-80% of the price of a new device.

Is it possible to leave the refrigerator to work without a relay if it starts?

Categorically no. The starting relay is necessary to create torque at start, and the thermal relay protects against overheating. Operation without them will lead to burnout of the windings or a fire within a short time.

Why does the engine hum but does not start when connected directly?

Most likely, the piston group is jammed due to lack of lubrication or mechanical wear. It is also possible that the starting winding may break, which creates the initial rotation impulse.

Which device is best suited for testing?

The optimal choice is a digital multimeter with a continuity mode and resistance measurement up to 2000 Ohms. Analogue testers are less convenient due to the difficulty of reading exact values.

Is it dangerous to carry out such a test yourself?

Yes, it is dangerous due to the high voltage of 220V. Inexperienced users are better off turning to professionals, as the risk of electric shock is very high when working with exposed live contacts.