A sudden stop of operation of the refrigerator or its inability to maintain the set temperature is often accompanied by strange sounds or changes in the temperature of external elements. If you notice that the lower part of the unit, where compressoris located, has become significantly warmer than usual, this may indicate serious problems in the engine starting electrical circuit. One of the most common culprits of this behavior is the start relay, which is responsible for activating the motor.
Overheating of this small but critical component does not just happen. Under normal conditions, the relay may be slightly warm when turned on, but it should not be hot to the touch while the refrigerator is running. If a part becomes hot to such an extent that it is impossible to touch it, or makes cracking and clicking noises, this is a sure sign that the system is operating in emergency mode or has already failed. Ignoring this symptom can lead to burning of the compressor windings, which is a much more expensive breakdown.
In this article we will analyze in detail the physical and electrical causes of overheating, diagnostic methods and safe ways to replace the part. Understanding the principle of operation start-protection mechanism will help you avoid common mistakes during repairs. We will consider both the design features of various types of relays, as well as external factors influencing their temperature conditions.
The principle of operation and functions of the starting relay
The starting relay is an electromechanical switch that supplies current to the starting winding of the compressor motor only in the moment of its launch. As soon as the motor rotor reaches the required speed, the relay opens the starting winding circuit, and the engine continues to operate on the main winding. This process takes only a few seconds, but it is at this moment that the maximum current passes through the contacts, which inevitably causes the release of heat.
There are two main types of devices used in modern and old models of refrigerators: posistor and induction. Posistor relay (PTC) contains a ceramic element, which, when heated by current, sharply increases its resistance, essentially breaking the circuit. Induction models work due to an electromagnetic field, which draws in the core, closing the contacts, and when the current drops, the spring returns it back. Both types have their own temperature characteristics.
What is the difference between a posistor and an induction relay?
A posistor relay (PTC) has no moving mechanical parts inside the switch itself and works on the principle of changing the resistance of a ceramic element. An induction relay uses a coil and a movable core that physically opens the contacts. PTC resistors are considered more reliable and modern, but they can heat up more at the moment of operation.
It is important to understand that short-term heating of the relay housing is a normal situation. However, if the heat is not dissipated and accumulates, or if the relay remains energized for longer than the specified time, the temperature begins to rise exponentially. This often happens because the compressor cannot start on the first try, and the relay pulses again and again without having time to cool down.
Main reasons for relay overheating
The most common reason why refrigerator relays overheat is sticking of contacts or their burning. Over time, carbon deposits form on the surface of the contacts, which increases resistance to electric current. According to the laws of physics, an increase in resistance during the passage of current leads to increased heat generation. As a result, the relay begins to heat up even when it is turned off or at the moment the circuit opens.
The second important reason is a malfunction of the compressor itself. If the refrigerator motor is slow, has mechanical damage or problems with the windings, it consumes significantly more starting current. A relay designed for standard loads is forced to pass excessive current through itself, which leads to overload and overheating. In this case, replacing the relay will only give a temporary effect, and the situation will repeat.
It is also worth considering the condition of the wiring and the tightness of the contacts. Loose terminals or oxidized connections create additional resistance in the circuit. The heat generated at the point of poor contact is transferred to the relay body, creating a false impression that the component itself is faulty. Therefore, before replacing, always check the quality of the connection of the wires.
- 🔥 Sticking of contacts: Mechanical or electrical welding of the contacts prevents the circuit from opening, and the starting winding remains energized.
- 📉 Voltage drop: Low voltage in the network causes the relay to keep the circuit closed longer, trying to start motor.
- 🔌 Oxidation of contacts: The chemical reaction of metal with air increases resistance and causes local overheating.
Symptoms of a faulty start-up relay
You can determine that it is the relay that is the source of the problem by a number of characteristic signs. Often users notice that the refrigerator hums, but does not start, or starts for a couple of seconds and immediately stalls with a characteristic click. At this point, the relay housing may be so hot that it smells like burning plastic. This indicates that the device is operating at the limit of its capabilities.
Another symptom is the unit turning on and off cyclically. The compressor tries to start, the relay heats up, the thermal protection (if built-in) trips or opens due to overload, after which the cycle repeats. A visual inspection can also give results: if traces of soot, plastic melting or swelling are visible on the relay body, the part definitely requires replacement.
You should not ignore even weak signs of unstable operation. If you hear a rapid clicking noise coming from the back of the refrigerator, it means the relay is trying to start the compressor but is unable to. Prolonged operation in this mode is guaranteed to lead to failure of not only the relay, but also the motor-compressor itself, the repair of which can cost more than a new refrigerator.
Diagnostics and performance testing
Before going to the store for a new part, you need to make sure that it is faulty. For diagnostics you will need a multimeter. First of all, the refrigerator must de-energize be moved away from the wall to gain access to the compressor. Remove the rear protective panel and the casing covering the compressor to get to the relay.
Carefully remove the relay from the compressor contacts. Usually it is simply put on three pins and secured with a bracket or latches. Shake the part near your ear: if you hear knocking or rattling inside, it means that the insides are destroyed or torn off, and the relay is definitely faulty. Next, proceed to testing the contacts with a multimeter in resistance measurement mode.
☑️ Algorithm for checking the relay
When When checking a posistor relay, the resistance between the contacts must be within certain limits (usually from 10 to 100 Ohms, depending on the model). If the device shows infinity (open) or zero (short circuit), the part is faulty. For induction relays, the integrity of the coil winding and the mobility of the core are checked. If the core is jammed or the winding is burned out, the relay must be replaced.
Table of relay types and their characteristics
Different models of refrigerators are equipped with different types of starting devices. Understanding their characteristics helps you choose the right analogue for repairs. Below is a comparative table of the main parameters that can affect the temperature regime and operation of the device.
| Relay type | Principle of operation | Normal temperature | Common cause of failure |
|---|---|---|---|
| Posistor (PTC) | Crystal heating | Up to 130°C (short-term) | Destruction of the ceramic element |
| Induction | Electromagnet | Up to 80°C | Moving core sticking |
| Thermal | Bimetallic plate | Up to 90°C | Deformation plates |
| Combined | Start + Protection | Up to 100°C | Failure of protection |
When selecting a replacement, pay attention not only to the appearance, but also to marking Rated current and voltage must match the original. Using a relay with a lower rated current will lead to its rapid overheating and combustion, since it will not cope with the load of a particular compressor.
Instructions for replacing the starting relay
Replacing the starting relay is a procedure that is accessible even to a beginner, if you follow safety precautions. The main rule: all work is carried out only with the refrigerator completely disconnected from the network. You will need a new part, a screwdriver (possibly pliers) and a couple of minutes of free time. Make sure that the new component fully matches the markings of the old one.
Remove the old relay, remembering or photographing the position of the wires. In some models, the wires can be connected directly to the relay, in others, the relay is simply slipped onto the compressor contacts. If the wires are soldered, they will have to be carefully unsoldered, but most often a connector or push-on system is used. Install the new relay, fitting it tightly onto the compressor contacts, and secure with a bracket or spring, if provided by the design.
After installation, plug in the refrigerator. In the first seconds, you may hear a click and a startup hum - this is normal. Listen: if the humming stops and the cold sets in, it means the repair was successful. If after 10-15 minutes of operation the relay begins to get very hot again or extraneous sounds appear, immediately turn off the device and check the compressor for an interturn short circuit.
⚠️ Attention: If after replacing the relay the compressor hums but does not start, do not keep it turned on for more than 10-15 seconds. This may cause the motor windings to burn out. In this case, the problem most likely lies in the compressor itself or the freon circulation system.
Prevention and safety measures
To extend the life of the start relay and compressor, it is important to ensure proper operating conditions for the refrigerator. First of all, this concerns ventilation. The back of the refrigerator should be at least 10cm away from the wall to allow heat to dissipate freely. If the compressor operates in overheated conditions due to poor ventilation, the relay will also be subject to increased temperature stress.
Regularly clean the rear condenser grill of dust and pet hair. A condenser clogged with dust increases the pressure in the system, which increases the load on the compressor and, as a result, on the start relay. It is also recommended to periodically check the tightness of the door and the condition of the seal so that the compressor does not work non-stop.
Do not forget that frequent turning on and off of the refrigerator is also harmful. Try not to open the door unless necessary and do not place hot food in the chamber. All these factors affect the frequency of compressor starts, and therefore the life of the starting relay. Taking good care of equipment is the best prevention of breakdowns.
⚠️ Attention: Technical characteristics of refrigerators and requirements for spare parts may vary depending on the manufacturer and year of manufacture. Always check the part markings with the documentation for your specific model or consultation with an official service center.
Is it possible to repair a burnt-out relay or just replace it?
In most cases, repairing a relay is impractical. If a posistor burns out, replacing it requires selecting an element with identical characteristics, which is difficult and expensive. If the contacts are burnt, cleaning them will only give a temporary effect, since the cause of the soot (sparking) will remain. It’s easier and more reliable to buy a new relay, which is inexpensive and will ensure long-term operation of the refrigerator.
Why does a new relay immediately burn out after installation?
This is a sure sign that the problem is not in the relay, but in the compressor. Most likely, an interturn short circuit has occurred in the motor windings, or the piston mechanism has jammed. The compressor draws too much current, which melts the contacts of the new relay. In this case, diagnostics of the motor or its replacement is required.
How long can a refrigerator operate with a faulty relay?
Working with a faulty relay is extremely undesirable. If the relay gets hot but the refrigerator is running, this may last from a few days to a couple of weeks, but the risk of fire or compressor failure is very high. If the relay clicks and does not start the motor, the refrigerator will not work at all. Operation in this mode is prohibited.
Does the room temperature affect the heating of the relay?
Yes, directly. If the refrigerator is placed in a hot area (for example, in the kitchen near the stove or in the sunny side), the overall temperature in the compressor area increases. This impairs heat transfer from the relay, and it operates at higher temperatures, which shortens its life. Try to install the equipment in cool, well-ventilated places.
Do you need to lubricate the relay contacts during installation?
No, under no circumstances should you lubricate the starting relay contacts. Any lubricant (even conductive) can disrupt the sparking process or, conversely, cause contact sticking. Contacts must be dry and clean. If moisture or grease gets inside the relay, it will quickly break down.