A sudden stop in the operation of the refrigeration chamber often takes you by surprise, but the cause of the breakdown is not always an expensive compressor. In most cases, the problem lies in the engine starting system, namely in start relay. This small component is responsible for supplying voltage to the motor windings when turned on, and its failure is one of the most common reasons why the refrigerator hums but does not start.
Checking this element does not require deep knowledge in electronics, but it does require attentiveness and a basic set of tools. If you notice that the unit turns on for a couple of seconds, makes a clicking sound and turns off, or the compressor hums but does not start, then it becomes the first suspect. Self-diagnosis will allow you to avoid wasting time calling a technician and will help you understand whether the part really needs to be replaced. starting relay becomes the first suspect. Self-diagnosis will allow you to avoid wasting time on calling a technician and will help you understand whether the part really needs to be replaced.
Before starting any work, you must remember safety. A refrigerator is an electrical appliance powered by a 220-volt network. Multimeter, a screwdriver and gloves are the minimum kit you will need to perform an accurate diagnosis. In this article, we will analyze each step of the test so that you can confidently determine the condition of the unit.
The principle of operation and types of starting relays
To understand how to correctly ring a part, you must first understand what exactly we are checking. A start relay is essentially a switch that only supplies current to the compressor's start winding when it starts. As soon as the motor rotor reaches the required speed, the relay opens the circuit and the motor continues to operate on the main winding. There are two main types of such devices, and the method of testing them has its own nuances.
The first type is induction (electromagnetic) a relay. They are more often found in older models of refrigerators, such as Soviet ZIL or Biryusa. Inside such a device there is a coil and a movable core. When current is applied, the core retracts and closes the contacts of the starting winding. When the current drops (the engine has started), the core, under the influence of gravity or a spring, returns to its original position, opening the circuit.
Second type - posistor relay. These are more modern devices installed in refrigerators Indesit, LG, Samsung recent years of production. There are no moving mechanical parts. Instead, a temperature-sensitive element is used - a posistor. When voltage is applied, its resistance increases sharply due to heating, which actually breaks the circuit of the starting winding. The key difference between a posistor relay is the need to cool down (about 3-5 minutes) before turning it on again.
⚠️ Attention: Never try ring the relay while it is connected to the electrical network. Even if the refrigerator is turned off with a button, the plug must be removed from the socket. Residual voltage in the capacitors can lead to electric shock or damage to the multimeter.
External inspection and initial diagnostics
Before picking up measuring instruments, you should conduct a visual inspection. Often signs of a malfunction are visible to the naked eye. Remove the back panel of the refrigerator (or the plastic cover at the bottom, depending on the model) and get to the compressor. The relay is usually placed directly on the side terminal of the compressor and secured with a bracket or simply held in place by a tight fit.
Carefully remove the relay. If it's an induction device, shake it near your ear. If you hear a rattling or knocking sound, it means the core or contacts inside are broken. This is a sure sign that the part requires replacement. In the case of posistor models, inspect the case for melting, cracks or traces of burning.
Pay attention to the condition of the contacts. If black carbon deposits, oxidation or traces of sparking are visible on the terminals, this indicates that the relay was operating in emergency mode or was overheating. Also check the wires going to the relay: they should not be frayed or melted. Any mechanical damage to the insulation makes the operation of the device dangerous.
Necessary tools and preparation
For high-quality diagnostics, you will need a minimum set of tools that any home craftsman will have. The main device will be multimeter (tester). It allows you to measure the resistance of the circuit, which is the main criterion for checking the integrity of contacts and windings.
You will also need:
- 🔧 Screwdriver (Phillips or flat) for removing protective covers and terminals.
- 🧤 Dielectric gloves to protect hands from possible residual discharges and sharp edges.
- 🔦 Flashlight for illuminating hard-to-reach places in the compressor area.
- 🧹 Dry rags or brush to clean contacts from dust and dirt before checking.
Preparing the multimeter is simple: put it in resistance measurement mode (indicated by the Ω or "Ohm" icon). Select a measurement limit of 200 ohms or 2 kohms. Before touching the relay, connect the tester probes to each other: the device should show zero or a value close to zero. This will confirm the serviceability of the measuring device itself.
⚠️ Attention: If you are using a pointer analog tester, before starting work, be sure to perform a zero calibration by connecting the probes and tightening the corresponding screw on the device body.
Step-by-step instructions: how to ring a relay
The verification process depends on the type of device, so it is important to first determine what exactly you have in your hands. Remove the relay from the compressor and remove the protective plastic or metal casing to gain access to the internals. Be careful not to damage fragile elements.
If in front of you induction relay, find the coil. Test it with the multimeter probes. The resistance of a working coil is usually from 30 to 200 ohms, depending on the model. If the device shows infinity (one on the left side of the screen or no movement of the arrow), it means there is a break in the winding and the relay is faulty. Then check the contacts: in normal condition they should be open (resistance is infinite). If you close the contacts manually (by gently pressing on the mechanism), the circuit should ring (the resistance is close to zero).
For positor relay the procedure is simpler. It usually has three contacts: two for connection to the compressor and one for the phase input. Ring the circuit between the contacts. In a cold state, the resistance of the posistor should be low (from 3 to 50 Ohms). If the multimeter shows infinity or, conversely, zero (short circuit) between contacts that should not be connected directly, the part must be replaced.
☑️ Checklist for checking the relay
It is also important to check the feed-through contacts of the relay itself. Some models have moving parts inside that can get stuck. Lightly tapping the body against the palm can help identify mechanical defects, but the main method is measurement resistance. If the multimeter readings “float” or are unstable when touching the contacts, this is a sign of oxidation or poor contact.
What to do if the relay is intact, but the refrigerator does not work?
If a check with a multimeter shows that the relay is working (resistance is normal, mechanical damage no), the problem may be deeper. Often the compressor itself fails (interturn short circuit) or the thermostat. It is also worth checking the capacitor if there is one in the circuit. Do not rush to put everything back together if you are not sure of the diagnosis - it is better to double-check the contacts again.
Table of normal readings and faults
For ease of diagnosis, it is recommended to check the table of typical values. Remember that specific numbers may vary slightly depending on the manufacturer Danfoss, Start or Relay, but the order of magnitude remains similar.
| Test type | Good condition | Fault (replacement required) | Probable cause |
|---|---|---|---|
| Coil resistance (induction) | 30 - 200 Ohm | Infinity (∞) | Winding break |
| Thesistor resistance (cold) | 3 - 50 Ohm | Infinity or 0 Ohm | Thermal element burnt out |
| Contacts in open state | Infinity (∞) | 0 Ohm (Ringing) | Sticking contacts |
| Mechanical check | Clear click | Thud or silence | Destruction of the core |
If your measurements coincide with the "Fault" column, then buying a new part is the only way out. The relay cannot be repaired, as it is a disposable unit. Attempts to clean the contacts or glue the housing, as a rule, give a short-term effect and can lead to combustion of the compressor.
Common mistakes in diagnostics
Beginners often make mistakes that lead to incorrect conclusions. One of the most common is checking a relay that has not been removed from the compressor. In this case, you call the circuit through the motor windings, and the multimeter shows their resistance, and not the state of the relay itself. Always remove the relay for accurate diagnostics.
Another mistake is ignoring the posistor cooling time. If you just turned off the refrigerator and immediately started checking the posistor relay, it may show high resistance because it is still hot. Let it cool for at least 5-10 minutes at room temperature.
Also, do not rely solely on visual inspection. Even if the relay looks perfectly clean and intact, the thin wiring inside could have burned out or the properties of the posistor may have changed. Only a multimeter will give an objective picture.
⚠️ Attention: The technical characteristics of the relay may vary depending on the power of the compressor. When purchasing a replacement, pay attention not only to the appearance, but also to the markings (for example, 1/6 hp, 1/4 hp) indicated on the body.
Replacement and final assembly
If diagnostics have confirmed a malfunction, you must purchase an analogue. It is best to look for the part by the markings on the body of the old relay. Universal relays also exist, but they require careful wiring according to the attached diagram.
Installation is done in the reverse order. Push the relay onto the compressor terminals until it stops. Make sure it fits snugly and doesn't wobble. Attach the retaining bracket or strip. Connect the wires to the terminals, observing polarity if indicated. Assemble the protective casing and secure it.
After assembly, turn on the refrigerator. During the first minutes of operation, listen to the startup sound. The compressor should start working with a characteristic hum, after 1-2 seconds a quiet click should be heard (the starting winding is turned off), and the motor will continue to run smoothly. If after 5-10 minutes the refrigerator begins to gain cold, it means the repair was completed successfully.
Is it possible to temporarily start a refrigerator without a relay?
Technically, you can start the compressor directly, but this is extremely dangerous and is not recommended for long-term operation. The motor may burn out after a few minutes or hours due to lack of protection and improper starting mode. Use this method only for short-term pumping out of freon during disposal.
Why does a new relay burn out immediately after installation?
Most often, the reason lies in a malfunction of the compressor itself (turn-to-turn short circuit of the windings), which consumes too much current. It is also possible for the piston group to jam. In such cases, replacing the relay is only a temporary solution; repair or replacement of the compressor is required.
Where to buy a suitable relay?
It is better to look for original spare parts in specialized stores of spare parts for household appliances or from official dealers of the brand of your refrigerator. Universal analogues are also sold on electronics markets, but it is important to check the power and connection diagram.