Checking the refrigerator motor without a relay: step-by-step methods for home repairs

Introduction: when is a check without a relay needed and why is it risky

The refrigerator engine (compressor) is the heart of the cooling system. If it fails, the equipment stops freezing, and food spoils in a matter of hours. Typically, diagnostics are carried out using starting relay, which protects the windings from overheating and ensures correct startup. But what to do if the relay is burned out, lost, or you want to check the compressor itself separately from the circuit?

Checking without a relay is an extreme measure that requires an understanding of electrical circuits and compliance with safety precautions. Incorrect operation may result in short circuit, winding damage, or even fire. In this article we will analyze 5 safe ways diagnostics that are suitable for most models (Biryusa, Nord, LG, Bosch etc.), and also tell you what signs indicate a malfunction of the engine, and not a thermostat or freon leak.

Before you begin, please note: if you are not confident in your skills, it is better to contact to the master. However, for experienced users, our instructions will help you save on diagnostics and understand whether it is worth repairing the compressor or whether it is easier to buy a new one.

Signs of a compressor malfunction: when the engine is to blame, not the relay

Often users confuse a relay failure with a malfunction of the compressor itself. To avoid wasting time, first rule out other causes:

• 🔌 The refrigerator does not turn on at all —check the socket, plug and power cord. Perhaps the problem is in the power supply, and not in the engine.
• ❄️ The compressor hums, but does not freeze - this could be a freon leak, a clogged capillary tube or a thermostat malfunction.
• 🔥 The relay clicks, but the engine does not start - a classic sign of an interturn short circuit in the windings or a jammed piston.
• 🛠️ The compressor runs for 2-3 seconds and turns off —most likely, the protection is triggered due to overheating of the windings or a malfunction of the relay.

If you observe at least one of these symptomsit makes sense to check the engine separately. But first, make sure that:

1. The thermostat is working (call its contacts).
2. There is enough freon in the refrigerator (if the condenser tube does not heat up, a leak is possible).
3. There is no mechanical damage on the compressor (cracks, dents, traces of oil).

Preparation for testing: tools and safety measures

To diagnose a compressor without a relay you will need:

Important! Working with a compressor under voltage requires completely disconnecting the refrigerator from the network. Even if you are an experienced electrician, do not neglect safety precautions:

⚠️ Attention: When the compressor is directly connected to a 220V network without a relay, the risk of a short circuit increases 3 times. Use 5A fuse in a phase wire break or connect via laboratory autotransformer (LATR)if available.

If you do not have experience working with high voltage, limit yourself to testing the windings with a multimeter this is enough for initial diagnosis.

Disconnect the refrigerator from the outlet

Remove back cover (if the compressor is closed)

Take a photo of the relay connection diagram

Wear protective gloves

Prepare a multimeter (switch to ohmmeter mode)

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Method 1: Testing the windings with a multimeter (without feeding voltage)

This is the safest method that does not require a network connection. It will help to identify open or interturn short circuit in the windings.

Action algorithm:

1. Remove the starting relay from the compressor (usually it is mounted on latches or screws).
2. On the compressor, find three terminals:
   • C (Common) - common terminal;
   • S (Start) - starting winding;
   • R (Run) - working winding.

Ring the resistance between the terminals:

• C–S (starting winding) - usually 20–40 Ohm;
• C–R (working winding) - usually 10–20 Ohm;
• S–R is the sum of resistances C–S and C–R (if less, there is an interturn short circuit).
• Check the resistance between any terminal and compressor housing - it should be ∞ (infinity). If there is a value, the winding is “broken” to the housing.

Normal resistance values for different models:

Refrigerator brand	Resistance C–S (Ohm)	Resistance C–R (Ohm)
Atlant, Minsk	25–35	12–18
Indesit, Ariston	30–40	15–20
Stinol, Bosch	20–30	10–15
Saratov, Biryusa	18–25	8–12

If the resistance:

• 🔴 Equal to 0 —winding break;
• 🟡 Significantly below normal — interturn short circuit;
• 🟢 Within normal limits —windings are in good condition (the problem may be in the relay or mechanical part).

Method 2: Direct connection to a 220V network (for experienced)

This method allows you to check the mechanical health of the compressor whether the piston group is working, whether there is any jamming. Use it only if the continuity of the windings shows normal!

Procedure:

1. Disconnect the relay from the compressor.
2. Connect starting winding (S) i working winding (R) to the 220V network via fuse 5A:
   • Phase (L) - on S;
   • Zero (N) - on R;
   • The general terminal (C) remains free.

Apply voltage briefly (for 1-2 seconds!).

What should happen:

• ✅ The compressor has started and is running - the mechanics are fine, the problem was in the relay or thermostat.
• ❌ A hum is heard, but the shaft does not rotate —the piston or bearings are jammed (needs repair or replacement).
• ⚡ Sparks, smoke, burning smell —immediately turn off the power to the windings! are closed.

⚠️ Attention: Do not keep the compressor connected for more than 3 seconds without a relay! The starting winding is not designed for long-term operation and may burn out.

Method 3: Checking the current consumption (for accurate diagnosis)

If you have There is current clamps or a multimeter with a current measurement function, this method will help identify winding overload or problems with the piston group.

How to measure:

1. Connect the compressor to the network via a relay (if it is working properly) or directly, as in Method 2.
2. Measure the current in operating mode (after starting).
3. Compare with the nominal value (indicated on the compressor nameplate or in documentation).

Normal current indicators:

• 🟢 Rated current ±10% — the compressor is working;
• 🟡 Current above the norm by 20–30% —overload (possibly jamming or high pressure in the system);
• 🔴 The current is below the norm by 30% or more - windings are worn out or insufficient voltage.

Example for a compressor Danfoss NL6 (installed in refrigerators Stinol, Indesit):

• Rated current: 1.2 A;
• Permissible starting current: up to 5 A (at 1–2 seconds).

What to do if the current is too high?

If the compressor consumes more current than indicated in the passport, this may mean:

1. Mechanical resistance (piston jamming, bearing wear).

2. High pressure in the system (clogged capillary tube or too much freon).

3. Interturn short circuit in the windings (even if the continuity test showed normal).

In the first two cases, a refrigeration technician will help. In the third, only replacing the compressor.

Method 4: Diagnostics of the mechanical part (without electricity)

If the compressor does not start, but the windings are working, the problem may lie in mechanics:

• 🔧 Shaft jamming (due to rust or wear of bearings);
• 🛢️ Lack of oil (the compressor overheats and turns off);
• 💨 Air getting into the system (after incorrect refilling of freon).

How to check the mechanics:

1. Remove the relay and the compressor protective casing.
2. Carefully rotate the shaft compressor with a screwdriver by the pulley (if there is one) or manually by the coupling.
3. Rate the effort:
   • ✅ The shaft rotates smoothly, without jamming - the mechanics are working;
   • ❌ The shaft does not rotate or requires a lot of force - jamming or wear.

Check the oil level (through the inspection window, if there is one). The oil should be clean, without metal shavings.

If the shaft does not rotate, you can try unwed compressor:

1. Drain the freon (only if you have experience!).
2. Fill into the compressor 10-20 ml of kerosene or WD-40 through the filling pipe.
3. Leave for 1-2 hours, then try turning the shaft again.

⚠️ Attention: If after wedging the compressor starts working, but after a while it jams again, it must be replaced. This is a sign of critical wear of the piston group.

Method 5: Testing with a capacitor (alternative to a relay)

If you have one starting capacitor (for example, from a washing machine or fan), it can be used for single start of the compressor this will help. check whether the engine can reach operating mode.

Connection diagram:

1. Connect the capacitor in parallel with the starting capacitor winding (C–S).
2. Apply voltage 220V:
   • Phase (L) - on S;
   • Zero (N) - on R.

Apply power briefly (for 1–2 seconds).

Condenser capacity:

• For compressors with power up to 150 W — 15–25 μF;
• For compressors 150–300 W — 30–50 μF;
• For powerful models (Bosch, LG) — up to 100 uF.

If the compressor started and continued to work after the capacitor was turned off, the problem was in starting. relayIf not, there is a malfunction in the windings or mechanics.

What to do if the compressor is faulty: repair or replacement?

If diagnostics show that the refrigerator motor is inoperative, you have two options:

Compressor repair it is advisable only in three cases:

1. Mechanical failure (for example, jamming of a shaft due to lack of oil).
2. The refrigerator is a rare model, and a new compressor is difficult to find.
3. You are confident in the technician who will carry out the repair (there are reviews, a guarantee).

In all other cases replacement of the compressor is a more reliable solution. However, consider:

• 🔧 Compatibility freon (for example, R134a incompatible with R600a);
• 📏 Dimensions and fastenings (the compressor must be in the old place);
• ⚡ Power (do not take a compressor weaker than the original one).

FAQ: Frequently asked questions about checking a compressor without a relay

Is it possible to start a compressor without a relay on a permanent basis?

No, this is extremely dangerous! and protects it from overheating. Without a relay, the compressor will burn out within a few minutes due to lack of protection.

What to do if the winding resistance is normal, but the compressor does not start?

In this case, the problem may be:

1. Mechanical jamming of the piston;
2. Insufficient voltage in the network (check with a multimeter);
3. Malfunction of the thermostat or control board;
4. Freon leak (the compressor cannot create pressure).

Try to start the compressor directly (see Method 2) or check the mechanics (see Method 4).

What multimeter is needed to check?

An inexpensive multimeter with an ohmmeter mode (up to 200) is sufficient Ohm) and the ability to measure alternating voltage (up to 500V). Popular models:

• DT-830B (budget option);
• Mastech MS8268 (for professionals);
• UNI-T UT33D (optimal price/quality ratio).

The main thing is that the device shows accurate resistance with an error of no more than 2-3%.

Is it possible to check the compressor without removing it from the refrigerator?

Yes, but it is less convenient. You will need:

1. Disconnect the refrigerator from the network;
2. Remove the back cover;
3. Disconnect the relay from the compressor;
4. Test the windings with a multimeter right on the spot.

However, for For accurate diagnostics (for example, checking mechanics), it is better to remove the compressor.

What to do if after checking the compressor starts working, but the refrigerator does not freeze?

In this case, the problem is not in the engine, but in:

• 🧊 Leakage freon (refilling required);
• 🔄 Clogged capillary tube (needs cleaning or replacement);
• 🌡️ Faulty thermostat (does not give a signal to turn on);
• ❄️ Heat transfer problems (the condenser is dirty, the fan does not work).

Check whether the condenser is heating up (the grill at the back of the refrigerator). If it is cold, there is a problem in the freon circulation system.