How to correctly connect the start relay to the refrigerator compressor: step-by-step instructions with diagrams

When the refrigerator suddenly stops freezing and the compressor does not start or runs jerkily, the culprit is often the start relay. This small but critical element is responsible for starting the compressor engine, and its incorrect connection can lead to serious damage - from overheating of the windings to failure of the entire unit. In this article, we will look at how to correctly connect the start relay to the refrigerator compressor, avoiding typical mistakes, and what to do if, after connecting, the device does not work.

The material will be useful both for beginners who are faced with refrigerator repair for the first time, and for experienced craftsmen who want to refresh their knowledge. We will consider in detail relay types (induction, posistor, electronic), their differences, and also give step-by-step connection diagrams for different models of compressors - from Soviet DXM-5 to modern Embraco and Secop. We will pay special attention to fault diagnosis and safety measures, which are often ignored during self-repair.

Before starting work, make sure that the problem is in the relay, and not in the compressor itself or the thermostat. To do this, just check the resistance of the windings with a multimeter - if the values ​​differ greatly from the nominal ones (usually indicated on the compressor tag), the relay may have nothing to do with it. But if everything is in order with the windings, and the engine does not start, it’s time to deal with the connection.

1. Types of starting relays and their features

Starting relays for refrigerators are divided into three main types, each of which has its own design features and scope. Choosing the wrong relay is one of the main reasons for unsuccessful repairs. Let's look at them in more detail.

Induction relays (for example, RTK-X or RTP-1) - the oldest and most reliable type, which is still used in domestic refrigerators (Atlant, Biryusa). They work on the principle of electromagnetic induction: when the compressor starts, the current in the starting winding creates a magnetic field that attracts the contacts, completing the circuit. The main advantage is simplicity and maintainability. The downside is sensitivity to voltage surges and the need for precise adjustment.

Posistor relays (for example, 3TSR or 2TSR) - more modern and compact. Instead of mechanical contacts, they use posistor (a thermistor with a positive temperature coefficient). When heated, its resistance increases sharply, turning off the starting winding. Such relays are more reliable than induction ones, but cannot be repaired - if they break down, they are only replaced. Often found in refrigerators Samsung, LG and Indesit.

Electronic relays are the most modern and universal. They are controlled by a microcircuit that analyzes the current in the windings and optimizes the start of the compressor. Such relays (for example, EGR1 or QP2-4.5) are used in inverter refrigerators (Mitsubishi Electric, Panasonic) and provide a smooth start, reducing the load on the network. The downside is the high cost and complexity of diagnostics without special equipment.

• 🔧 Induction: reliable, but require configuration. Suitable for older models.
• 🔥 Posistor: compact, but not repairable. Popular in refrigerators of the 2000–2010s.
• 📱 Electronic: universal, but expensive. Used in modern inverter models.

⚠️ Attention: If you are replacing the relay on a refrigerator with an inverter compressor (for example, Hitachi or Toshiba), never install an induction or posistor relay instead of electronic. This will lead to a failure of the control algorithm and may burn the board.

2. Tools and materials for connection

Before you start work, prepare everything you need. The absence of even one tool can turn a simple procedure into agony. Here is the minimum set:

• 🔌 Multimeter (to check the resistance of the windings and relay circuit). Even a budget model like DT-830B.
• ⚡ Screwdrivers (cross and flat) is suitable for dismantling the compressor cover and mounting the relay.
• 🔗 Wires with a cross-section of 0.75–1.5 mm² (if you need to replace damaged contacts). It is better to use stranded copper.
• 🧲 Soldering iron and solder (for restoring burnt contacts or terminals).
• 📏 Pliers and stripper (for stripping wires).
• 🛡️ Dielectric gloves (for safety when working under voltage).

You may also need heat shrink tube to insulate connections or terminal blocks, if the relay and compressor contacts do not match in size. For diagnostics of electronic relays it is useful oscilloscope, but you can do without it if you are sure of a malfunction.

If you If you are working with a refrigerator using refrigerant R600a (isobutane), make sure that there is no open flame nearby - this gas is highly flammable. For models with R134a or R12 the risk is less, but ventilation of the room is still necessary.

3. Connection diagram of the starting relay to the compressor

Before connecting the relay, you need to understand how the electrical circuit of the compressor works. Most models have three terminals:

1. Common (C) —connected to both windings.
2. Working winding (Main, M or Run, R) —the main winding of the motor.
3. Start winding (Start, S) —used only for starting.

The relay is connected between starting winding and common output, and the working winding is connected directly to the network. Below is a typical circuit for an induction and posistor relay:

For clarity, we will give an example of connecting an induction relay RTK-X to the compressor DXM-3:

1. Connect the wire from the socket to the terminal L relay.
2. Connect the second wire of the socket to the working winding (M) of the compressor.
3. From the C relay terminal, stretch the wire to the common terminal (C) of the compressor.
4. From the relay starting terminal (S) connect the wire to the terminal S of the compressor.

If you are working with a posistor relay, the connection procedure is simplified: all three terminals of the compressor are connected to the corresponding terminals of the relay (C, M, S), and power is supplied to the terminals L i N.

Take a photo of the original connection diagram|Test the compressor windings with a multimeter|Make sure that the voltage in the network is stable (220V ±10%)|Check the integrity of the relay wires-->

4. Step-by-step instructions for connecting

Now let's move on to practice. Follow the instructions carefully - an error at any stage can lead to a short circuit or failure of the compressor.

Step 1: Disconnecting the refrigerator from the network

This seems obvious, but many forget to unplug the plug from the socket before starting work. Even if the compressor is not working, the capacitors in the circuit can retain a charge, which will lead to an electric shock. It is additionally recommended to discharge the capacitor, by shorting its terminals with a screwdriver with an insulated handle.

Step 2: Removing the old relay

Remove the compressor protective casing (usually it is attached to latches or screws). Carefully disconnect the wires from the relay terminals, after photographing or sketching the connection diagram. If the wires are oxidized or burnt, it is better to replace them.

Step 3: Checking the compressor

Before installing a new relay, make sure that the problem is not in the compressor. Test the windings with a multimeter:

• Resistance between C and M: usually 10–30 Ohms (working winding).
• Resistance between C and S: usually 20–50 Ohms (start winding).
• Resistance between M and S: the sum of the two previous values (30–80 Ohms).

If the values are very different or tend to infinity, the winding is broken. If close to zero, there is a short circuit. In both cases, the compressor requires repair or replacement.

Step 4: Installing a new relay

Follow the connection diagram (see section 3). If you are using a universal relay (for example Danfoss 103N0240), make sure that it is compatible with the power of your compressor (indicated on the tag). The relay must be firmly attached to the compressor - vibration can lead to broken contacts.

Step 5: Checking operation

After connecting, turn on the refrigerator. The compressor should start without any extraneous sounds (knocking, humming). If the relay clicks, but the engine does not start, check:

• The correct connection of the wires.
• The voltage in the network (must be at least 200V).
• The integrity of the starting capacitor (if it is in the circuit).

5. Typical mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes when connecting the starting relay. Let's look at the most common of them and ways to prevent them.

Error 1: The starting and operating windings are mixed up

If you swap the wires S i M, the compressor will either not start or will work in the opposite direction side (which is physically impossible, but will lead to overheating). Always check the diagram on the compressor tag or in the documentation.

Error 2: Using a relay with inappropriate parameters

The relay is designed for a certain starting current (indicated on the housing, for example, 4.5A or 6A). If you take a relay with a lower rating, the contacts will burn. If it is large, the compressor may not start due to insufficient current in the starting winding.

Error 3: Poor contact at the terminals

Oxidized or loose terminals lead to heating and burning. All connections must be clean and securely fastened. For reliability, you can solder the contacts.

Error 4: Ignoring checking the compressor

When installing a new relay on a faulty compressor (for example, with an interturn short circuit), you risk immediately burning both the relay and the motor. Always check the windings before connecting.

Error 5: Working without grounding

The refrigerator is a device with a metal body. If there is no grounding in the connection diagram, you may receive an electric shock if the insulation breaks down. In modern homes, this is solved through a Euro socket with a grounding contact.

⚠️ Attention: If after replacing the relay the compressor starts, but after a few seconds it turns off, the problem may be in thermal relay or jammed engine. Do not try to start it again without diagnostics - this will lead to overheating.

What to do if the relay clicks, but the compressor does not start?

This is a typical sign of a faulty starter winding or turn-to-turn short circuit. Check the resistance between terminals C and S - if it is below 15 ohms or approaches zero, the compressor is faulty. Also, the cause may be low voltage in the network (less than 190V) or a faulty capacitor (if there is one in the circuit).

6. Diagnostics of faults after connection

If after connecting the relay the refrigerator does not work or does not work correctly, it is necessary to carry out diagnostics. Here is the verification algorithm:

1. The relay clicks, but the compressor does not start:

• 🔌 Check the voltage in the socket (should be 220V ±10%).
• 🔧 Ring the starting winding (C–S). If there is a break, the compressor is faulty.
• ⚡ Check the starting capacitor (if any). Its capacity must correspond to the nominal value (usually 10–40 μF).

2. The compressor starts, but immediately turns off:

• 🌡️ Check the thermal relay - perhaps it opens the circuit due to false operation.
• 🔥 Measure the current in the operating winding. If it is higher than the nominal value (indicated on the compressor tag), the motor is overloaded.
• 🛠️ Check the condenser fan (if equipped) - overheating may cause a shutdown.

3. The relay gets hot or smells like burning:

• 🔥 Turn off the power immediately! This is a sign of a short circuit or overload.
• 🔧 Check the resistance of the windings - possibly an interturn short circuit.
• ⚡ Make sure that the relay is suitable for the current. For example, for a 140W compressor you need a rating of at least 5A.

If the diagnostics did not reveal any problems, but the compressor still does not work, it may be faulty control board (in modern refrigerators) or thermostat (in older models). In this case, it is better to contact a specialist.

7. Connection features in refrigerators of different brands

The design and connection diagram of the relay may differ depending on the manufacturer of the refrigerator. Let's consider the nuances for popular brands.

Atlant, Biryusa, Minsk (Belarusian/Russian models):

• Most often used induction relay type RTK-X or RTP-1.
• Compressors usually have standard pin markings: C, S, M.
• In older models there may be no starting capacitor - its role is played by the relay itself.

Samsung, LG (Korean refrigerators):

• Mainly positor relays (for example, 3TSR-OL).
• In inverter models they are used electronic relays with control from the board.
• Compressors often have non-standard connectors - an adapter may be required.

Indesit, Ariston (European brands):

• Relays are often found Danfoss or Embraco.
• In some models, the relay is integrated with start-up capacitor.
• The pin markings may differ: instead of C-S-M Hitachi are used, Mitsubishi (Japanese refrigerators) Com-Start-Run.

Hitachi, Mitsubishi (Japanese refrigerators):

• Almost always electronic relays with soft start.
• Compressors often have built-in protection against overheating.
• Replacing the relay requires setting parameters through the service menu (in inverter models).

⚠️ Attention: In refrigerators No Frost with two compressors (for example, Samsung RL-60), each relay is connected separately. - a sure way to disable both motors.

8. When is it better to contact a specialist

Not all breakdowns can be repaired yourself. Here are the cases when you should call a specialist:

• 🔧 If after replacing the relay the compressor buzzes, but does not start - this may indicate on engine jammed or piston group malfunction.
• ⚡ If it works when turned on automatic machine in the panel there is probably a short circuit in the windings or breakdown on the body.
• 🧊 If the refrigerator does not freeze, but the compressor works the problem may be freon leak or clogged capillary tube.
• 📱 If the refrigerator with electronic control gives an error (for example, E1 or F5) - required diagnostics of the board.

Also, do not take risks if you are not confident in your skills in working with electricity. An error during connection can lead not only to breakdown of the refrigerator, but also to fire or electric shock.

The average cost of replacing a relay in a service center is from 1500 to 3000 rubles (in depending on the refrigerator model and relay type). If you have already bought a relay and tried to install it yourself, but nothing worked, the technician will only charge for the work (usually 1000–1500 rubles).

FAQ: Frequently asked questions about connecting the start relay

Is it possible to connect a relay from one refrigerator to another?

Theoretically, it is possible, but only if they match:

• Relay type (induction/positionstor/electronic).
• Rated current (indicated on the relay body and compressor tag).
• Connection diagram (number and location of terminals).

For example, relay from Atlanta suitable for Biryusyif both refrigerators use compressors DXM-5 with an induction relay RTK-X. But a relay from Samsung with a posistor is not suitable for Indesit with an electronic relay.

How to test a relay without a compressor?

You can assemble a test circuit:

1. Connect the relay to a 220V network through an incandescent light bulb (power 60–100W) in series with the working winding of the compressor (or resistor 20-30 Ohm).
2. When power is applied, a working relay should click and close the circuit (the light will light up).
3. After 1-2 seconds the contacts should open (the light will go out).

If the relay does not click or The light does not light up - it is faulty. For posistor relays, the test is more complicated - you need a multimeter in resistance testing mode (the posistor must change resistance when heated).

What happens if you connect the relay incorrectly?

The consequences depend on the type of error:

• If you mix it up starting and operating windings - the compressor will not work will start, but the relay will click.
• If you connect a relay not of this type (for example, a posistor instead of an induction one), the compressor may burn out due to incorrect starting current.
• If you connect incorrectly power (for example, change the phase and zero) - the relay may work, but the compressor will work unstably.
• If you leave exposed wires - there is a risk of a short short circuit and fire.

In the best case, the refrigerator simply will not turn on. In the worst case, the compressor will burn out or a fire will occur.

What should the relay temperature be during operation?

Normal values:

• Induction relay: up to 50–60°C (if hot, check the contacts).
• Posistor relay: up to 70–80°C (the posistor heats up during operation).
• Electronic relay: up to 40–50°C (overheating indicates a board malfunction).

If the relay heats up to 90°C and above, this is a sign of:

• Short circuit in the compressor windings.
• Inconsistencies between the rated current of the relay and the compressor.
• Poor contact in the terminals (oxidation, weak tightening).

It is possible Is it possible to start a compressor without a relay?

Technically yes, but only for short-term testing. To do this:

1. Connect the working winding (C–M) directly to the 220V network.
2. Briefly (for 1-2 seconds!) connect the leads with a wire C–S (start winding).
3. The compressor should start. After starting, the starting winding can be turned off.

⚠️ Attention: Long-term operation without a relay will lead to overheating of the starting winding and failure of the compressor! This method is only suitable for diagnostics.