The situation when the refrigerator Nord stops cooling, and the compressor is either silent or hums for a couple of seconds and clicks, most often indicates a malfunction of the start-up protection relay (PPR). This small but critical element is responsible for starting the engine and protecting the windings from overheating. If you are faced with a similar problem, replacing the relay yourself can be a quick and economical solution that does not require calling a technician.
However, before starting disassembly, it is important to make sure that the reason lies in the relay, and not in the motor-compressor itself. Start-up protection device is a consumable item, which wears out over time, losing its physical properties. In this article we will analyze in detail the process of diagnostics, selection of an analogue and correct installation of a new PZR on Nord brand refrigerators.
You must understand that electricity is dangerous, and any work should be carried out only after the device has been completely disconnected from the network. Incorrect connections or the use of an incompatible part can result in the failure of an expensive compressor. We will consider all the nuances so that you can carry out repairs safely and efficiently.
Diagnostics of a malfunction of the start-up protection relay
The first sign of failure of the PZR is the characteristic behavior of the motor. You can hear the refrigerator trying to turn on: there is a hum that lasts 3-5 seconds, followed by a loud click and silence. This means that the relay is trying to start the engine, but cannot, and the thermal protection is tripping. In some cases, the compressor may be hot to the touch, although the refrigerator inside is warm.
To accurately diagnose the problem, it is necessary to visually inspect the part. After removing the casing and removing the relay, pay attention to its appearance. If traces of burning, melted plastic, or the smell of burnt wiring are visible inside the case, then PZR malfunction it is obvious. It is also worth checking the contacts for oxidation, which often interferes with the normal flow of current.
⚠️ Attention: If after replacing the relay the situation has not changed and the compressor continues to hum and turn off, the problem may lie in the interturn short circuit of the motor windings. In this case, professional diagnostics are required with measurement of winding resistance.
Sometimes the cause may not be the relay itself, but a jammed compressor. To eliminate this, you can try (short-term!) applying voltage directly, but this should only be done by experienced craftsmen. For the average user, the safest way is to replace the relay with a known good one. If a new part does not help start the unit, then the problem is deeper.
Preparation of tools and selection of an analogue of the PZR
For a successful replacement, you will need a minimum set of tools. First of all, these are flat-head and Phillips screwdrivers for removing the compressor protective casing. Terminal removal pliers and a multimeter may also come in handy if you decide to test the circuit before installing a new part. Don't forget to prepare a dry rag to clean the contacts.
The most important step is choosing the right analogue. Relays Nord can be equipped with various types of PZR depending on the year of manufacture and model of the compressor. There are always markings on the body of the old part. The most common models are RTK, R-3, R-4 or more modern LS, R6. It is critically important to select a relay with identical operation current and connection type (horizontal or vertical).
Modern relays are often universal and suitable for several models of compressors, but you need to focus primarily on the engine power and the location of the contacts. If you buy a relay with a different cut-off current, it either will not start the motor or will not protect it in case of overload, which will lead to the windings burning out.
- 🔧 Screwdrivers (flat and Phillips) for removing the casing.
- 🔌 Pliers or side cutters for working with terminals.
- 📷 Smartphone for photographic recording of the connection diagram.
- 🧹 Dry rags and alcohol for cleaning contacts.
Dismantling the old start-protective device
The dismantling process begins with ensuring safety. Unplug the refrigerator's power cord from the outlet. Only after this can you begin to remove the rear protective panel at the bottom of the case. It is usually secured with latches or several screws. By removing the panel, you will gain access to the compressor.
On the back of the motor you will see a plastic casing covering the electrical part. It must be carefully removed by squeezing the latches or unscrewing the screw. Under the casing there is the relay itself, mounted on three pins of the compressor. Before removal, be sure to take a photo of how the wires are connected so as not to confuse them during assembly.
Sequence of actions for dismantling:1. Disconnect the refrigerator from the network.
2. Remove the rear cover of the unit.
3. Remove the plastic casing from the compressor.
4. Take a photo of the wire connection diagram.
5. Remove the terminals from the relay contacts.
6. Carefully pull the relay off the compressor pins.
Remove the relay carefully, without sudden jerks, so as not to damage the suitable wires. If the terminals are oxidized and difficult to remove, you can slightly warm them with a hairdryer or carefully clean them. Put the old device aside; it will no longer be needed, unless you plan to conduct laboratory tests of its insides.
☑️ Ready for dismantling
Connection diagram and installation of a new relay
Installation of a new PZR is carried out in the reverse order of dismantling. The main rule: the relay is put on the compressor pins in only one position. If you try to put it on incorrectly, it simply won't seat all the way or the pins won't line up. Do not use excessive force; it is better to double-check the orientation of the part.
Pay attention to the contact markings. Usually on the relay body there are designations: M (Main) - main winding, S (Start) - starting winding, and phase input. On the compressor pins, they may also be marked or have different diameters. An error in connecting the starting and working windings can lead to instant combustion of the new part.
| Relay type | Compressor power | Cut-off current | Position |
|---|---|---|---|
| RTK-1 | up to 120 W | 1.3 A | Vertical |
| RTK-2 | up to 160 W | 1.6 A | Vertical |
| P-3 | up to 180 W | 1.8 A | Horizontal |
| LS-07B | universal | 1.4-1.6 A | Any |
After the relay is put on the pins, you need to connect the wire terminals. Make sure they fit snugly and don't wobble. If the contact is weak, the connection point will begin to heat up, which will lead to repeated failure. Then return the plastic casing to its place and secure the back panel of the refrigerator.
What to do if the new relay does not fit in the seats?
In some cases, when replacing old Soviet relays with modern universal ones, minor modifications may be required. For example, if the holes in the new relay are wider, you can carefully tighten them with pliers or use heat shrink to secure them to the pins. The main thing is to ensure tight contact and immobility of the part.
Checking functionality after replacement
After assembling all components, you can proceed to testing. Plug in the refrigerator. In the first seconds you will hear a startup hum, which after 1-2 seconds should turn into a smooth, quiet hum of a running engine. There should not be a shutdown click. If the compressor started working and began to gain cold, it means replacing the PZR it was successful.
Listen to the operation of the unit for 10–15 minutes. There should be no extraneous vibrations, knocking or intermittent humming. It is also worth checking the heating of the relay itself - it may be warm, but not hot. If the relay heats up to such an extent that it is painful to touch, it means that the cut-off current has been selected incorrectly or there is a problem with the compressor.
⚠️ Attention: If after turning on the refrigerator worked for several minutes and turned off again with a click, immediately unplug it from the network. Repeated starting attempts can completely kill the compressor. In this case, a re-check of the circuit or consultation with a specialist is required.
Make sure that the cold has begun to build up in the refrigerator and freezer compartments. This may take from 30 minutes to several hours, depending on the model Nord and the number of products loaded. Complete cooling to the set temperature usually occurs within 24 hours.
Typical errors when connecting PZR
One of the most common mistakes is ignoring the condition of the wires. When changing a relay, many people forget to check the cables suitable for it. If the insulation is melted or the copper is blackened, contact will be poor even with a new part. In such cases, it is necessary to strip the wires or extend them using high-quality soldering, and not just twisting.
An error with the orientation of the relay in space is also common. Some PZR models are position sensitive (the arrow on the body should point up or down). If you install a vertical relay horizontally, the thermal release may not operate correctly, or the starting winding will not turn off in time.
- ❌ Installing the relay without checking the coincidence of the current characteristics.
- ❌ Ignoring oxidation on the contact terminals.
- ❌ An attempt to start a compressor with an open electrical part.
- ❌ Using relays from refrigerators of a different power (for example, from a two-chamber to a single-chamber).
Remember that saving on the quality of the relay can backfire. Cheap Chinese analogues often have a variation in cutoff current, which makes their operation unpredictable. It is better to buy an original spare part or a proven analogue from a well-known manufacturer than to risk expensive compressor repairs.
⚠️ Attention: Technical characteristics of refrigerators may vary depending on the modification. Always check the markings on the nameplate of your device and the parameters of the old relay before buying a new one.
Questions and answers (FAQ)
Is it possible to repair an old PZR or just change it?
Theoretically, a starting relay (with a posistor or coil) can be try to disassemble and clean the contacts if the problem is oxidation. However, the thermal protection (bimetallic plate) loses its properties over time and gets tired. Therefore, the repair is temporary, and it is safer to completely replace the unit.
Why does a new relay burn out immediately after installation?
This can happen for several reasons: the cut-off current is incorrectly selected (the relay is too weak), the compressor is jammed (the motor cannot turn and takes a huge current), or there is a problem in the wiring (short circuit). It is also possible that the new relay itself is defective.
Where can I find the relay markings if they are erased?
If the markings on the body are not readable, you will have to select an analogue according to the compressor model. Find the sticker on the motor itself (usually silver or white), write down the model (for example, Danfoss NL7.5F, Atlant, etc.) and power. Using these data, you can find a suitable PZR in the spare parts catalogs.
How long does the starting relay last?
The average service life of the PZR is 5–10 years, but it greatly depends on the number of on-off cycles and the stability of the voltage in the network. Frequent power surges and temperature changes in the room can shorten this period.