How to start the engine from a refrigerator: a complete guide

The situation when the refrigerator stops cooling, and the compressor is silent or only makes a click, is familiar to many owners of household appliances. Often this indicates a failure of start relay or the thermostat, but the motor itself may be completely fine. The ability to start the engine directly is a critical diagnostic skill, allowing you to separate costly compressor failure from cheap sensor replacements.

Before taking active steps, you must completely protect yourself and the environment. Working with electric current and refrigerant requires strict adherence to safety precautions and an understanding of the operating principles asynchronous motors. In this article we will analyze in detail the algorithm of actions, the necessary tools and typical mistakes that beginners make when trying to revive an old refrigerator.

Principle of operation and device compressor

The heart of any refrigeration unit is a hermetic compressor, inside which an electric motor and a piston group are located. Most household models use single-phase asynchronous motors with a squirrel-cage rotor. The peculiarity of such motors is that they cannot start on their own without creating an initial torque.

To create this torque, there are two windings in the motor stator: the main (working) and auxiliary (starting) windings. The main winding creates a magnetic field, and the starting winding shifts the phase, creating the necessary impulse to start the rotor. As soon as the engine picks up speed, the starting winding must be turned off, otherwise it will burn out due to overload.

A special device is responsible for the process of turning the starting winding on and off - start relay. In older models it can be electromagnetic, in modern ones it is most often posistor (thermal). Understanding this “winding-relay” connection is key to successful diagnosis.

Necessary tools and precautions

Diagnostics and starting the compressor require a minimum set of tools, which most home craftsmen can find. However, the lack of professional equipment is compensated by increased attention to detail. You will need:

• 🔧 A set of screwdrivers (phillips and flat) for removing the casing.
• 🔌 A multimeter or tester for checking the windings.
• 🔌 Wires with alligator clips for temporary connection.
• 🧤 Dielectric gloves for protection against electric shock.

Particular attention should be paid to the condition of the wiring and insulation. If you see melted wires or smell a burning smell, start the engine strictly prohibited before replacing the damaged areas. It is also important to make sure that there is at least a minimum amount of freon or nitrogen in the system, since running the compressor “dry” (without pressure) is only permissible for a short-term check and can lead to scuffing in the piston group.

⚠️ Attention: Never start the compressor if oil comes out of the pipes or a strong whistle is heard air suction - this may indicate a violation of the tightness of the circuit or a lack of refrigerant, which will lead to rapid failure of the unit.

It is better to work in a well-ventilated area. Although freon is not dangerous in a working circuit, if there are leaks, the concentration of gases can be unpredictable. In addition, a running compressor gets very hot, so do not touch metal parts during the test.

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Diagnostics of motor windings with a multimeter

The first stage of the test is to assess the integrity of the electrical circuit of the windings. To do this, you need to remove the back cover of the refrigerator, get to the compressor and carefully remove the start relay along with the thermal relay. Below them you will see three contact pins forming a triangle.

Switch the multimeter to resistance measurement mode (Ohms) to the 2 kOhm limit. Call pairs of contacts. In a working engine, you should get the following values:

Pair of contacts	Expected resistance	Value
Working - Common	10 - 30 Ohm	Low resistance
Starting - General	20 - 50 Ohm	Medium resistance
Working - Starting	Sum of two previous	Highest value
Any contact - Housing	Infinity (1)	No short circuit

If the device shows one (infinity) between any two winding contacts, that means in the engine open circuit. It is impossible to restore such a motor at home. If the resistance between the contacts and the body shows any value (not infinity), this means insulation breakdown to the body. Operating such a unit is deadly.

Why is the resistance of the starting winding higher?

The starting winding is wound with a thinner wire and has more turns than the working one, so its resistance is always higher. This is normal for asynchronous motors.

Direct starting circuit without a relay

The most reliable way to check the performance of the motor is to start it directly, bypassing the standard relay. This allows you to exclude a malfunction of the starting device and check the mechanical and electrical parts of the engine. To implement this scheme, you will need a piece of wire with a plug and two separate wires with clamps.

The algorithm of actions is as follows:

1. Identify the common contact (usually it is located separately from the pair or marked with a letter C / Common).
2. Connect one wire from the power plug to the common contact.
3. Connect the second wire from the plug to the contact of the working winding.
4. To start, you need an impulse to the starting winding: briefly touch the wire from the network to the contact of the starting winding.

At the moment of contact, the rotor should jerk and start. After starting, the wire from the mains will start. the starting winding must be removed immediately, the engine will continue to operate on the working winding. Be careful: with this connection, the engine is deprived of thermal protection, so you cannot keep it turned on for a long time.

☑️ Checking direct starting

Common contact is determinedWorking winding is connectedA short-term impulse has been applied to the starterThe engine has picked up speedThe current is normal

Done: 0 / 5

If the engine hums, but does not start even when a pulse is applied to the starter the winding may have been jammed by the piston group or a turn short has occurred. In this case, further resuscitation requires opening the housing, which is not practical at home.

Checking and replacing the starting relay

Often the problem lies not in the engine itself, but in the relay, which does not supply the required impulse Visually. inspect the device: if a ringing sound is heard inside (the posistor is broken) or traces of burning are visible, it needs to be replaced. However, sometimes the relay can be “revitalized” or checked.

Electromagnetic relays (old type) operate on the principle of closing a contact when the current increases. If the contacts inside are burnt, the engine will hum, but will not start. You can try to carefully clean the contacts with a fine cloth. sandpaper, but this is a temporary measure. When heated, posistor relays (plastic cube) increase the resistance and open the circuit. You can check the posistor with a multimeter: in a cold state it should have low resistance, when heated with a hairdryer it should go to infinity.

⚠️ Attention: When installing a new relay, make sure that it matches the markings of the old one. Installing a relay with a different operating current can lead to combustion. windings or inability to start the compressor.

Replacing a relay is a simple procedure: remove the old one, remember the position of the contacts and install the new one until it clicks. Make sure the relay is tight and not loose, as vibration can break contact.

Typical errors and troubleshooting

In the diagnostic process, beginners often make mistakes that can lead to false conclusions or damage to equipment. One of the most common is incorrect identification of contacts. By mixing up the work and start windings, you can get humming and overheating instead of rotation.

Another common problem is ignoring the condition of the capacitor (if there is one in the circuit). Some refrigerator models use capacitor start. If the capacitor is swollen or has lost capacity, the motor will not receive the required phase shift. The capacitor is checked visually (for swelling) and with a device (capacitance measurement).

It is also worth remembering the time factor. If you kept the refrigerator in a horizontal position for a long time during transportation, oil may have leaked into the circuit. Starting such a compressor immediately after installation can lead to water hammer. Let the equipment stand vertically for at least 4-6 hours.

Frequently asked questions (FAQ)

Is it possible to start a three-phase motor from a refrigerator in a single-phase networks?

Theoretically it is possible using a circuit with capacitors, but for household refrigerators this is impractical. Compressors for domestic refrigerators are initially designed as single-phase. Three-phase motors are found in industrial equipment, and their conversion requires complex calculations of capacitor capacity.

Why does the compressor hum but does not start?

This is a classic sign of a jammed piston group ("wedge") or a malfunction of the starting relay. It is also possible that there is a voltage drop in the network or a short circuit in the windings. Try the direct start method: if it doesn’t help, most likely the motor needs to be replaced.

How long can you keep the compressor on when checking?

Without a connected capacitor and in open air conditions (without cooling the case), the compressor can be kept on for no more than 1-2 minutes. It heats up quickly, and the lack of heat removal can damage the insulation of the windings.

Is it dangerous to breathe freon vapors during testing?

Short-term inhalation of small amounts of freon (R134a or R600a) usually does not cause severe poisoning, but can cause dizziness. However, R600a (isobutane) is explosive at concentrations in air greater than 1.3%. Therefore, the check should be carried out in a ventilated area, away from open fire.