Connecting a refrigerator motor without a relay: step-by-step guide with diagrams

Connecting the refrigerator compressor directly, bypassing starting relay, is a task encountered when diagnosing malfunctions or temporarily restoring the operation of equipment. Most often, this method is used when the relay has failed and there is nothing to replace it with, or you need to check the performance of the motor itself. However, this process requires an understanding of electrical circuits and strict adherence to safety precautions: errors can lead to damage to the windings, a short circuit or even a fire.

In this article we will look at how to correctly identify compressor contacts, assemble a temporary connection diagram and avoid common mistakes. It is important to note that constant operation of the refrigerator without a relay inadmissible is a temporary solution for testing or emergency mode. If you do not have experience working with electrical equipment, it is better to contact a specialist.

⚠️ Warning: Working with high voltage electricity (220V) is life-threatening. All manipulations are carried out only with the power turned off and using protective equipment (insulated tools, dielectric gloves).

1. When is a connection without a relay required?

Direct connection of a refrigerator compressor is relevant in several cases:

• 🔧 Diagnostics of a relay malfunction. If the refrigerator does not turn on and the motor does not show signs of life, a test without a relay will help determine whether the relay itself or the problem is in the compressor.
• ⚡ Emergency start. When the relay burns out and there is no new one at hand, you can temporarily connect the motor directly to save food from spoilage (for example, at the dacha).
• 🔍 Checking compressor windings. If the motor hums but does not start, a direct connection helps identify an interturn short circuit or break.
• 🛠️ Repair in the field. In workshops, they sometimes use this method to quickly check compressors removed from equipment.

However, it is important to understand the limitations: without a relay, the motor will operate without protection from overheating and power surges. Long-term operation in this mode reduces the life of the compressor by 2-3 times.

⚠️ Attention: If the refrigerator is under warranty, any interference with the electrical circuit will void the manufacturer's warranty. Check the conditions in the product passport.

2. Refrigerator compressor design: what contacts you need to know

To connect the motor correctly, you need to understand its design. The refrigerator compressor has three outputs (contacts), which are usually marked or arranged in a standard order:

• 🔌 C (Common) - common contact. Connected to the working and starting windings.
• 🔄 S (Start) - starting winding. Used only to start the engine.
• 🏃 R (Run) - working winding. Ensures continuous operation after starting.

In most models (Danfoss, Embraco, Secop) the contacts are located in the shape of a triangle. The general contact (C) is often located at the top, and S and R on the sides. However, some compressors (for example LG or Samsung) may have different markings or color coding of the wires.

If there are no markings, you can determine the contacts using a multimeter:

1. Measure the resistance between all pairs of contacts.
2. The highest resistance is between S and R (the sum of the resistances of both windings).
3. The lowest is between C and R (working winding).
4. Average value - between C and S (starting winding).

Example of resistances for an Embraco EG80HLC compressor

Working winding (C-R): 5–7 Ohm
Start winding (C-S): 10–12 Ohm
Total (S-R): 15–19 Ohm

⚠️ Attention: For inverter compressors (for example, LG Linear Compressor or Samsung Digital Inverter) circuit connection is different. They are not intended for direct starting without an electronic control unit. An attempt to connect them directly will lead to irreversible damage.

3. Necessary tools and materials

To safely connect a compressor without a relay, you will need:

• 🔌 Multimeter (to check resistance and voltage).
• 🔧 Insulated screwdrivers (flat and cross).
• ⚡ Wires with a cross-section of 1.5–2.5 mm² with female terminals (for reliable contact).
• 🛡️ Dielectric gloves (protection against electric shock).
• 🔌 Extension cord with grounding (for ease of connection).
• 📏 Pliers/stripper (for stripping wires).
• 🔥 Heat shrink tube or electrical tape (for connection insulation).

Additionally, the following may be useful:

• 🔍 Magnifying glass or flashlight (for inspecting the markings on the compressor).
• 📝 Notepad (for recording resistances and connection diagrams).
• 🔋 UPS (uninterruptible power supply) - if there are frequent power surges in the network.

⚠️ Important: Do not use wires with damaged insulation or twisted without rations. Poor contact can cause heating and melting.

4. Connection diagram for a compressor without a relay: step-by-step instructions

Before starting work be sure to disconnect the refrigerator from the network and discharge the capacitors (if they are in the circuit). Next, follow the algorithm:

Step 1: Disconnecting the relay

Remove the start relay from the compressor. It is usually secured with latches or screws. Carefully disconnect the wires, remembering or photographing their location. The relay may have a connection diagram - save it.

Step 2: Identifying contacts

As described above, identify the contacts C, S i R using a multimeter. If the compressor is new, markings can be applied to the housing.

Step 3: Preparing the wires

Strip the ends of the wires (5-7 mm) and put terminals on them. Connect:

• One wire from the plug to the contact C.
• The second wire from the plug to the contact R.
• Connect the contacts briefly (for 1-2 seconds) S and C with a separate wire to start.

Critical detail: the starting wire (S-C) should only touch the contacts during startup. A prolonged short circuit will lead to overheating of the starting winding.

Step 4: Test run

Connect the plug to the network. Briefly close S i C and the motor should start. If the compressor hums but does not rotate, re-close the contacts. If it does not start, there may be a malfunction of the windings or a mechanical blockage.

Step 5: Disconnection

After checking, immediately disconnect the compressor from the network. Long-term operation without a relay is dangerous!

⚠️ Attention: If smoke, sparks or a burning smell appears during startup, immediately turn off the power. These are signs of a short circuit or interturn breakdown.

5. Typical mistakes and how to avoid them

Even experienced craftsmen sometimes make mistakes when connecting a compressor directly. Here are the most common ones:

• ❌ Incorrect identification of contacts.
  Consequences: The motor does not start or the starting winding burns out.
  Solution: Always check the resistance with a multimeter.
• ❌ Long S-C circuit.
  Consequences: Overheating and failure of the starting winding.
  Solution: Close the contacts for no longer than 2 seconds.
• ❌ Use of thin wires.
  Consequences: Heating, melting of insulation, short circuit.
  Solution: Wire cross-section - at least 1.5 mm².
• ❌ Work without grounding.
  Consequences: Risk of electric shock due to insulation breakdown.
  Solution: Use a grounded socket or RCD.
• ❌ Ignoring mechanical faults.
  Consequences: The motor may start, but quickly overheat due to jamming.
  Solution: Check whether the compressor shaft rotates freely (with the power off).

Another common problem is reverse rotation of the shaft. If the motor spins in the opposite direction, swap the wires to S and R. However, in refrigerators with a hermetic compressor, this is unlikely, since the shaft is rigidly connected to the crank mechanism.

What to do if the motor starts and immediately stops?

This may indicate:
1. Low voltage in the network (less than 200V).
2. Malfunction of the piston group (wear of rings, valves).
3. Blockage in the capillary tube (high discharge pressure).
Diagnostics require pressure gauges and experience in working with refrigeration equipment.

6. Safety measures: what not to do

Working with a refrigerator compressor falls into the category of dangerous electrical operations. It is strictly prohibited:

• ⚡ Connect the compressor without a safety circuit breaker.
  Use a 10-16A circuit breaker to protect against short circuits.
• 🔌 Start the motor without fixing.
  The compressor must be firmly secured - vibration can damage the tubes or tear them off wires.
• 🔥 Use an open flame for soldering near the compressor.
  There may be flammable refrigerant left in the system (for example, isobutane R600a).
• 💧 Work in wet conditions.
  Water + electricity = high risk of electric shock.
• 🛠️ Disassemble the sealed compressor.
  This will lead to freon leakage and irreversible damage.

⚠️ Warning: If you feel a burning smell or you see blackening on the contacts of the compressor, do not try to start it. These are signs of internal damage to the windings. Further operation may lead to a fire.

Also remember that in some models of refrigerators (for example, No Frost with inverter control) the compressor is integrated. into the electronic system. Its direct connection without a control unit is impossible.

7. Alternative methods of starting without a relay

If you do not have the opportunity to assemble the circuit manually, you can use temporary solutions:

• 🔄 Using a starting capacitor.
  Connect a capacitor (for example, 25–50 µF, 450V) between S and R. This simulates the operation of a relay with a posistor.
• 🔧 Connection via a button.
  Install the button without fixing into the wire gap between S and C. Press it to start, release after start.
• 🔌 A temporary relay from other devices.
  A relay from an old air conditioner or washing machine is suitable (if the parameters match).

For inverter there are no alternatives to compressors - they require an original control unit. Attempts to start them “bypassing” lead to the combustion of the power electronics.

⚠️ Attention: Starting capacitors must be designed for alternating current (marking ACUsing electrolytic capacitors for direct current will lead to their explosion.

Frequently asked questions

Is it possible to constantly operate a refrigerator without a relay?

No. The starting relay not only starts the motor, but also protects it from overheating, power surges, and in some models - from reverse motion of the shaft. Constant operation without a relay reduces the life of the compressor by 2-3 times and can lead to a fire.

How to check if the relay is working?

Disconnect the relay and check it with a multimeter:

1. In normal condition between the contacts C and R there must be resistance (usually 5–20 Ohms).
2. When voltage is applied to the relay coil, the contacts S and C should close.

If the contacts do not close or “stick”, the relay is faulty.

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

This is a typical sign:

• Faulty start relay (most often).
• Interturn short circuit in the windings.
• Mechanical blocking (shaft jamming, valve failure).

Try to start the motor without a relay, as described in the article. If this does not help, the compressor must be replaced.

Is it possible to connect it? compressor from the refrigerator to another voltage (for example, 110V)?

No. Refrigerator compressors are designed for a strict voltage (usually 220-240V, 50 Hz). Connecting to 110V will lead to:

• Low power (the motor will not be able to create the required pressure).
• Overheating of the windings (due to increased current).

To operate from 110V, you need a transformer or autotransformer with the appropriate characteristics.

Where to buy a new relay for a refrigerator?

The relay can be found:

• In refrigerator repair service centers (they often sell used spare parts).
• In online stores (for example, AliExpress, eBay - search by compressor model).
• In electronics stores (universal type relays 3-pin RBM or PTC).

Cost - from 300 to 1500 rubles depending on the type.