Sudden stoppage of the compressor or chaotic humming of the refrigerator Nord often indicates problems in the electrical engine starting circuit. Equipment owners are faced with a situation where the engine hums but does not start, or turns on for just a few seconds and immediately turns off. In most such cases, the culprit is a failed one starting relay, which is responsible for supplying voltage to the windings.
Independent testing of this unit does not require deep knowledge in electronics, but requires compliance with safety precautions and the availability of a minimum set of tools. It is important to understand that the relay is a mechanism that wears out naturally, and replacing it is a normal maintenance procedure. In this article we will look at how to accurately determine the malfunction without resorting to the services of a service center.
Before starting disassembly, you need to make sure that the refrigerator is disconnected from the power supply. Failure to do so may result in electric shock or electronic damage due to accidental short circuit. Diagnostics will take no more than 30 minutes if you follow the algorithm of actions.
Signs of a faulty trigger mechanism
The first step in diagnosis is to observe the behavior of the unit. If compressor it makes a characteristic beep, twitches, but the rotor does not start rotating, this is a classic symptom of “sticking” or destruction of the contacts inside the relay. Sometimes the process is accompanied by clicks that are repeated at certain intervals.
Another important sign is operation thermal protection. If the motor heats up and turns off by the circuit breaker 10-20 seconds after turning it on, it means that the current in the circuit exceeds the permissible limits. This often happens when the relay contacts have oxidized and cannot pass the necessary impulse to start.
It is also worth paying attention to the appearance of the part. If during a visual inspection you find traces of burning, melted plastic, or an unpleasant smell of burnt insulation, then the relay definitely requires replacement. In rare cases, the problem may lie in the compressor itself, but checking the relay is the primary stage of malfunctions.
⚠️ Attention: If after replacing the relay the situation has not changed and the compressor continues to hum without starting, the motor itself may have jammed or a “breakdown” of the windings has formed. Further attempts to turn on may permanently damage the unit.
Even short-term malfunctions should not be ignored. Periodic starting attempts create a colossal load on the motor windings, which reduces its service life. Timely replacement of an inexpensive relay will save an expensive compressor from burning out.
Design and types of relays in Nord refrigerators
In brand refrigerators Nord, as in most classic models, two main types of starting devices are used: induction (electromagnetic) and posistor. Understanding how they work will help you better navigate the verification process. Induction relays operate due to the electromagnetic field that is created when current passes through the coil.
When the starting current exceeds a certain value, the coil core is retracted and closes the contacts of the starting winding. As soon as the engine picks up speed, the current drops, and the core, under the influence of gravity (or a spring), opens the circuit. Posistor analogs operate differently: they use a semiconductor element, which is heated by the current and sharply increases its resistance, opening the circuit.
- 🔌 Induction relays are often marked RTP, RTK or R-1 and require correct orientation during installation (arrow up).
- 🔥 PTC elements (marked 33OM or similar) are more compact, do not depend on position and are considered more reliable in modern conditions.
- ⚙️ A protective relay (thermal) can be built into the trigger housing or be a separate element that responds to temperature and current.
It is important to note that in older models Nord there is often a combination of two separate blocks: a trigger and a protective one, connected by an adapter frame. In newer versions, these components can be combined into a single plastic housing. When searching for a spare part, you must take this design feature into account.
You can determine the type of your relay by its appearance. If you see a heavy coil with copper winding and a moving core inside the housing, it is an electromagnetic type. If there is a small ceramic or plastic disk with contacts there, it is a posistor. Replacing one type with another is possible, but requires careful selection of parameters.
Is it possible to install a relay from another brand?
Yes, you can often use analogues if the mounting dimensions and electrical characteristics match. The main thing is that the rated current and type of contacts correspond to the original. However, it is better to look for original spare parts or proven cross-codes.
Preparation for diagnostics and dismantling
To carry out a quality test, you will need a minimum set of tools. The main device will be multimeter (tester), which allows you to measure resistance and check the integrity of the circuit. Without this device, accurate diagnostics is impossible, since it is impossible to determine the state of the internal contacts by eye.
Also prepare a flat-head and Phillips screwdriver, pliers and, possibly, a knife for stripping the contacts. Before starting work, be sure to unplug the refrigerator and move it away from the wall, providing access to the rear panel. The compressor must cool completely to avoid burns and distortion of the thermal relay readings.
The dismantling process begins with removing the compressor protective casing. It is usually secured with latches or bolts. After removing the cover, you will see a black “tank” of the compressor, at the end of which there is a plastic box attached - this is the relay you are looking for. It is fixed on three pins coming out of the compressor.
☑️ Preparation for checking the relay
Carefully disconnect the wires going to the relay. It is recommended to first take a photo of the connection diagram so as not to confuse the contacts during assembly. Remove the retaining bracket or frame holding the relay to the compressor and pull the plastic housing down, releasing the pins.
Step-by-step test with a multimeter
The removed relay must be opened. Depending on the model, the housing may be held together with screws or plastic clips. Be careful not to damage the fragile plastic. Inside you will see contacts, a coil (or posistor) and moving elements.
The initial check is carried out visually. Look for signs of carbon deposits, blackening or destruction of contacts. If the contacts are burnt, you can try to clean them with fine sandpaper, but this is a temporary measure. For accurate diagnostics, switch the multimeter to resistance measurement mode (Ohm).
Checking the electromagnetic relay:
- 📏 Measure the coil resistance - it should be within normal limits (usually several tens of Ohms), a break indicates a malfunction.
- 🔄 Check the moving core: in a horizontal position the contacts should be open, and when turned over (imitation of switching on) - close.
- ⚡ Ring the thermal relay: in a cold state it should ring (resistance is close to zero), when heated, open the circuit.
Checking a posistor relay is even simpler. A posistor at room temperature should have a low resistance (20-50 Ohms). If the multimeter shows infinity (open) or zero (short circuit), the element is faulty. Also check the integrity of the bimetallic plate of the thermal release.
Table of faults and troubleshooting methods
To systematize data on possible problems, use the following table. It will help you quickly compare the device readings with the type of failure and determine further actions.
| Symptom | Multimeter readings | Probable cause | Solution |
|---|---|---|---|
| Compressor buzzes, does not start | The coil resistance is infinite | Breakage of the electromagnet winding | Replacing the relay |
| Clicks and turns off | Contacts do not ring when closed | Soot or sticking contacts | Cleaning or replacement |
| The motor does not turn on at all | Thermal relay does not ring (cold) | Thermal relay burnt out | Replacing the thermal element |
| Chaotic operation | The posistor resistance is normal | Mechanical jamming of the core | Lubrication or replacement |
If diagnostics showed that the relay OK, but the refrigerator does not work, the problem may be deeper. The compressor itself may be faulty (turn-to-turn short circuit) or the wiring may be faulty. In such cases, you cannot do without the help of a specialist with professional equipment.
When replacing a part, make sure that the new relay has identical characteristics. The compressor power and starting current must match. Installing an unsuitable relay can lead to rapid failure of the new part or damage to the engine.
Assembly and final testing
After successful diagnosis or replacement of the component, proceed with assembly. Install the relay on the compressor pins exactly in the position in which it was removed. For electromagnetic relays, this is critically important: the arrow on the body must point up, otherwise the mechanism will not work.
Attach the fixing frame and connect the wires according to the photographs or diagram taken earlier. Make sure all connections are tight and not loose. Put on the compressor protective casing and screw the back panel of the refrigerator.
Plug in the refrigerator and listen. Start-up should occur with a characteristic click, followed by the even hum of a running motor. If after 10-15 seconds there is no shutdown and coldness appears in the chamber, the repair was successful.
⚠️ Attention: In the first minutes of operation, a new or restored compressor may operate a little louder than usual. This is normal, but if the noise persists for more than 30 minutes or is accompanied by vibration, immediately turn off the device.
It is recommended to periodically check the temperature in the chambers during the first day and monitor the cyclic operation of the unit. This will help ensure the stability of the repair.
Frequently asked questions (FAQ)
Is it possible to solder the relay contacts instead of replacing them?
Theoretically, you can strip the contacts or even solder them tightly for testing, but this is a temporary solution. Factory contact coating (silver or special alloys) ensures reliable sparking. Soldering with regular tin will create transition resistance, which will quickly lead to burning and repeated failure. It is better to replace the part.
Why does the relay burn out constantly?
Frequent combustion of the relay may indicate problems with the compressor itself (difficult starting, bearing wear) or voltage surges in the network. The cause may also be incorrect installation of the relay (incorrect orientation). It is recommended to check the voltage in the network and the condition of the motor windings.
Where to find the markings of the relay for replacement?
The markings are usually applied to the side or top edge of the plastic relay case. Look for type designations RTP, RTK, 33OM or manufacturer codes such as Danfoss, Secop. Also, the spare part number can be found in the technical documentation of the refrigerator Nord.
Is it dangerous to operate a refrigerator with a broken relay?
It is strictly forbidden to turn on the compressor without a start relay or with shorted contacts. This will cause the starting winding to burn out in a matter of seconds, since it is not designed for long-term operation. The compressor will fail completely.