How to correctly connect the refrigerator relay 103N0021: diagrams, errors and tips installation

The relay 103N0021 is one of the most common start-up protection elements in domestic and foreign-made refrigerators. Its task is to start the compressor and protect the windings from overheating. But what to do if the relay has failed, and you only have a new device at hand without instructions? Connect it incorrectly —this means risking burning the compressor or causing a short circuit.

In this article we will look at step-by-step connection of relay 103N0021from contact identification to testing performance. We will pay special attention to typical mistakes that even experienced professionals make. And if your refrigerator model is non-standard, you will find a compatibility table with analogues.

Before you take up a soldering iron or screwdriver, make sure that the problem is in the relay. Characteristic symptoms malfunction:

• 🔊 The compressor hums, but does not start (protection is triggered).
• ⚡ The refrigerator turns on for 1-2 seconds and immediately turns off.
• 🔥 A burning smell or melted plastic appears on the relay body.
• ❄️ The temperature in the chambers does not drop to the required level.

1. Design and operating principle of relay 103N0021

The relay 103N0021 belongs to start-protective current relay (PZR) and consists of two functional parts:

1. Starting block —short-term closes the starting winding of the compressor to create an initial torque.
2. Protective block - opens the circuit when the compressor overheats or jams (triggered by current or temperature).

Inside the case located bimetallic plate, which heats up when a current passes above the rated current. When the current exceeds the permissible threshold (for example, when the compressor shaft is jammed), the plate bends and opens the contacts. In normal mode, the relay closes the circuit working winding and for 1-3 seconds connects starting winding through the capacitor.

Technical characteristics of relay 103N0021:

⚠️ Attention: Relay 103N0021 has several modifications with different rated current (for example, 103N0021-10 and 103N0021-20). Connecting a relay with a lower current than the compressor requires, will lead to false protection activations.

2. Preparation for connection: tools and safety measures

Before starting work be sure to unplug the refrigerator and defrost the condensate on the relay body or compressor. may cause a short circuit. You will need:

• 🔧 Phillips screwdriver (to remove the compressor cover).
• 🔌 Multimeter (to check the windings and relay contacts).
• 🔗 Pliers or side cutters (for crimping terminals).
• 📏 Voltage tester (optional, for checking power supply).
• 🧊 Electrical tape or heat shrink tube (for insulating connections).

Sequence preparation:

1. Move the refrigerator away from the wall to gain access to the compressor.
2. Remove the bottom decorative panel (if any) or back cover.
3. Inspect the relay for melting, cracks or rust.
4. Take a photo current connection of wires - this will help avoid installation errors.

If there are signs of overheating on the relay body, do not try to repair it - just replace itthe bimetallic plate and the contacts inside cannot be restored at home. conditions.

3. Connection diagram for relay 103N0021: step-by-step instructions

Standard relay 103N0021 has 3 or 4 contacts depending on the modification). Let's consider both options.

Contact designations:

• 1 (L) —phase (220V power supply).
• 2 (M) —output to the working winding of the compressor.
• 3 (S) — output to the starting winding (via a capacitor).
• 4 (N) — zero (in 4-pin relays).

Connection diagram for a 3-pin relay:

1. Contact 1 (L) connect with the phase wire of the network (usually brown or red).
2. Contact 2 (M) connect to the working winding of the compressor (C or Main).
3. Contact 3 (S) connect to the starting winding (S or Start) through starting capacitor (if it is provided by the circuit).

Scheme for a 4-pin relay:

1. Contact 1 (L) i 4 (N) connect to the 220V network (phase and zero).
2. Contact 2 (M) - to the working winding.
3. Contact 3 (S) - to the starting winding (through a capacitor, if any).

The compressor box usually has winding markings: C (Common) — common terminal, S (Start) — starting winding, R (Run) —working winding.

How to find the windings if there are no markings?

If the marking is erased, use a multimeter in ohmmeter mode:

1. Measure the resistance between all pairs of contacts.

2. The highest resistance is between S And R (starting + working windings).

3. The lowest is between C and S or C and R (common terminal + one of the windings).

⚠️ Attention: If your refrigerator is equipped with starting capacitor, its cannot be connected directly to relay. The capacitor should be connected only to the starting winding (S) and one of the relay terminals. (3). Connecting a capacitor to the phase (L) will lead to a short circuit!

4. Checking the relay and compressor before connecting

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

1. Switch the multimeter to ohmmeter mode (200 Om).
2. Measure the resistance between the compressor terminals:
   • C–S: 20–40 Ohms (starting winding).
   • C–R: 10–20 Ohms (working winding).
   • S–R: 30–60 Ohms (sum winding resistance).

If at least one value is equal to 0 (short circuit) or ∞ (open), the compressor is faulty.

Checking relay 103N0021:

• Ring the contacts 1–2 (in normal state - open).
• Apply 220V voltage to 1–4 (for 4-pin) or 1–2 (for 3-pin through a light bulb 40 W).
• When voltage is applied, a click should be heard - this is the contacts of the starting circuit closing.

1. Connect the relay to the compressor according to the diagram.

2. Insert the refrigerator plug into the outlet for 1-2 seconds.

3. If the relay is working properly, the compressor should start with a characteristic hum.

4. If you hear clicks, but the compressor does not spin, the problem is in the windings or capacitor.-->

5. Typical connection mistakes and how to avoid them

Even experienced technicians sometimes make mistakes that lead to repeated breakdowns. Let's look at the most common ones:

Error 1: The starting and operating windings are mixed up

If you connect S instead of R, the compressor will try to start "in the opposite direction", which will lead to shaft jamming or protection activation. How to check: after connection, the compressor should hum smoothly, without rattling.

Error 2: There is no contact in terminals

Poorly crimped or oxidized wires cause false protection trips. All connections must be securely fastened and insulated.

Error 3: Incorrect relay rating

Relay with response current 1.5 A is not suitable for a compressor for which necessary 2.5 A. As a result, the relay will operate at the slightest load.

Error 4: Ignoring the capacitor

If the refrigerator circuit is provided starting capacitor, it required needs to be connected. Without it, the starting winding will not receive the required impulse, and the compressor will not start.

6. Compatibility of relay 103N0021 with different refrigerators

The relay 103N0021 is suitable for most refrigerators with compressors with power up to 140 W. However, there are nuances:

Compatible brands and models:

• 🏭 Atlant: series MHM, NOU FROST (DXM-3, DXM-5 compressors).
• 🏭 Indesit: models with compressors Danfoss NL/NF (for example, Indesit B18FNF).
• 🏭 Stinol: refrigerators STINOL 101/103 with compressors Secop (Danfoss).
• 🏭 Biryusa: series 3K, 6K (DXM compressors).

Incompatible cases:

• Refrigerators with inverter compressors (for example, LG Linear, Samsung Digital Inverter).
• Models with electronic control boards (requires an original relay with a Hall sensor).
• Compressors with a higher power 160 W (requires a relay with a current >3 A, for example, 103N0041).

⚠️ Attention: In refrigerators No Frost with two compressors (for the refrigerator and freezer compartments) for each compressor you need separate relayConnecting one relay for two compressors will lead to the output of both. building.

If your refrigerator model is not listed in the list, check the compressor characteristics with the table below:

7 Analogs of relay 103N0021 and theirs. features

If the original relay 103N0021 cannot be found, you can use analogs. The main thing is the match in rated current and type of mounting.

Popular analogues:

• 🔄 DXR-3 —complete analogue, suitable for DXM compressors.
• 🔄 RBM-1 —universal relay for Danfoss and Secop.
• 🔄 LRS-08B —for compressors Embraco (fastening needs modification).
• 🔄 3TS-2 - Chinese analogue, but with a shorter resource.

How do the analogues differ:

When choosing an analogue, pay attention to:

1. Type fastening (clip or screw).
2. Rated current (must match or be higher than the original).
3. Presence of a protective cap (cheap analogues often do not have it, which reduces safety).

8. Testing after connection: what to check first

After installing the relay 103N0021 do not rush to close the refrigerator. Check procedure:

1. External inspection: make sure that all wires are connected tightly, there are no exposed areas.
2. First turn on:
   • Connect the refrigerator to the network.
   • The compressor should start with a slight hum (no clicking or rattling).
   • After 1-2 minutes, check if the condenser is heating up (should be warm, but not hot).

Checking the temperature:

• After 1-2 hours operation, check whether the refrigerator is freezing.
• If the compressor turns off too often (every 5-10 minutes), perhaps the relay does not match the current.

Signs of incorrect connection:

• 🔊 The compressor hums, but does not start (the windings are reversed or not capacitor).
• ⚡ The relay clicks every 5-10 seconds (insufficient operating current).
• 🔥 The relay body heats up to >60°C (poor contact or short circuit in the windings).

⚠️ Attention: If after replacing the relay the compressor works, but the refrigerator does not freeze, the problem may be freon leakage or clogged capillary tube. In this case, diagnostics of the cooling system will be required.

FAQ: Frequently asked questions about the 103N0021 relay

Is it possible to connect a relay? 103N0021 without a capacitor?

No, if the refrigerator circuit provides starting capacitor. Without it, the starting winding will not receive the required impulse, and the compressor will not start. The exception is models with built-in capacitor in the compressor (for example, some Danfoss NF).

What is the difference between relays 103N0021-10 and 103N0021-20?

The main difference is nominal response current:

• 103N0021-10: 1.0–1.5 A (for compressors up to 100 W).
• 103N0021-20: 1.8–2.5 A (for compressors 120–160 W).

Connecting a “weak” relay to a powerful compressor will lead to frequent shutdowns.

Why does the new relay click, but the compressor does not start?

Probable reasons:

1. Confused starting and working windings.
2. Faulty starting capacitor (test it with a multimeter - the resistance should drop from ∞ to 0).
3. The compressor shaft is jammed (try turning it manually by turning off the power).

Is it possible to repair relay 103N0021?

Theoretically, it is possible replace bimetallic plate or clean the contacts, but in practice this is impractical. The cost of a new relay (~300–500 rubles) is comparable to the cost of repair, and the reliability of the repaired device will be lower.

Which relay is suitable for the Atlant MXM refrigerator 1705?

For this model with a compressor DXM-5 suitable:

• 103N0021-10 (original).
• DXR-3 (analog).
• RBM-1 (universal, but you will need to bend the mount).

The main thing is the operating current is not less than 1.5 A.