A sudden stop of the refrigerator compressor often confuses the owner, causing him to panic about food spoilage. However, in many cases, the cause of the breakdown is not the motor itself, but a faulty starting relay, which is responsible for starting the engine. Self-diagnosis of this element allows you to save a significant amount on calling a technician and quickly return the equipment to working order.
To carry out an accurate check, you will need a minimum set of tools, the main one of which is multimeter. This device allows you to measure the resistance of the windings and check the integrity of the contacts, which gives an unambiguous answer about the condition of the part. It is important to understand that relays come in different types, and the approach to testing them may differ slightly depending on the design.
In this article we will examine in detail the process of removing, visually inspecting and electrically testing the starting device. You will learn how to interpret tester readings and what nuances to pay attention to when diagnosing. Correctly following all the steps will help you accurately determine whether the refrigerator needs to replace the spare part or whether the problem lies deeper.
Operating principle and design of the starting relay
The starting relay is an electrical switch that supplies voltage to the starting winding of the compressor only at the moment of startup. As soon as the engine reaches the required speed, the relay opens the circuit and the refrigerator continues to operate on the main winding. This mechanism is critically important, since without an initial impulse the motor rotor simply cannot move.
There are two main types of devices: posistor and induction. Posistor ones models work due to the properties of a ceramic element, which is heated by current and increases resistance, opening the circuit. Induction ones use an electromagnetic coil and a movable core, which lowers under the influence of gravity after the motor starts.
⚠️ Attention: An attempt to replace an induction relay with a posistor one (or vice versa) without changing the connection diagram can lead to the compressor burning out. Always use parts with a similar operating principle.
Understanding the internal structure helps you quickly find contacts for dialing. In induction models, the contacts open mechanically, which is often accompanied by a characteristic click. PTC elements do not have moving parts in the classical sense; their operation is based on changes in the physical properties of the material when heated.
Preparation for diagnostics and safety measures
Before proceeding with disassembly and testing, it is necessary to completely de-energize the refrigerator. Unplug the cord from the outlet and make sure there is no voltage at the compressor terminals. Working with electrical appliances requires compliance with basic safety rules, since even after disconnection, a charge may remain in the capacitors.
To work, you will need a multimeter, a set of screwdrivers, pliers and, possibly, electrical tape for marking the wires. It would also be a good idea to prepare photo camera or a smartphone to photograph the wiring diagram before disconnecting them. This will help avoid errors during assembly.
☑️ Preparing to check the relay
Access to the relay is usually located in the lower rear part of the refrigerator, where the compressor is located. You may need to remove the protective plastic cover or cardboard panel. Be careful with the refrigeration circuit tubes - they are thin and easily damaged if handled carelessly.
Dismantling and visual inspection of the part
Remove the terminal block from the compressor contacts by first unsnapping the fixing clips or unscrewing the screws. Carefully remove the relay itself, which is usually simply attached to the three pins of the compressor. Try not to pull sharply so as not to damage the suitable wires.
The first stage of diagnosis is thorough visual inspection. Shake the relay near your ear: if a rattling sound is heard inside, this is a sure sign that the contacts or the posistor have crumbled. In this case, the part definitely requires replacement, and checking with a multimeter may no longer be necessary.
Inspect the case for melting, blackening or cracks. The presence of carbon deposits on the contacts indicates a spark has slipped and a poor connection. If you see traces of burning or smell burning plastic, this indicates an overload or short circuit inside the device.
Why does the relay burn out?
A frequent cause of failure is not the relay itself, but problems with the compressor. If the motor is “difficult” to start due to wear or problems with the freon circuit, the starting device takes on an increased load and burns out. Therefore, replacing the relay without eliminating the root cause may lead to repeated failure in a short time.
Checking the relay with a multimeter: step-by-step instructions
To carry out measurements, switch the multimeter to the resistance measurement mode (Ohm), usually in the range of 200 Ohms or 2 kOhms. If you have an induction relay, place it in the correct position (as it is on the compressor), since the contacts close under the influence of gravity. In an inverted state, the circuit may be open.
Find the contacts corresponding to the starting winding. In most cases, they are located in a certain way, but it is better to check the markings on the case or the diagram. Apply the multimeter probes to the contacts: if the device shows one (infinity), then the circuit is broken. If it shows zero or a value close to zero, the circuit is intact.
For posistor relays, the procedure is slightly different. You need to check the resistance between the contacts to which the posistor is connected. It should be within normal limits (usually several tens or hundreds of ohms). If the multimeter shows an open or short circuit, the element is faulty. Also check the integrity of the coil, if it is present in the design.
⚠️ Attention: When checking the induction relay in the inverted position (contacts open), the multimeter should show a break. If you see resistance in this position, the contacts are stuck and the relay needs to be replaced.
It is also important to check the resistance between the relay body and any contacts. It should be in good condition break. The presence of resistance indicates an insulation breakdown, which is dangerous for operation and requires immediate replacement of the part.
Table of faults and instrument readings
Measurement results can be interpreted differently depending on the type of relay and the position of the probes. Below is a summary table that will help you quickly diagnose the condition of the element.
| Test type | Multimeter reading | Probable cause | Action |
|---|---|---|---|
| Posistor (contacts) | Infinity (1) | Open circuit, posistor burnt out | Replacement of relay |
| Posistor (contacts) | Zero (0) or small number | Normal (cold posistor) | Good |
| Induction (normal position) | Zero (0) | Contacts closed | Normal |
| Induction (inverted) | Zero (0) | Sticking contacts | Replacement of relay |
| Any relay (case) | Any value | Breakage to the case | Urgent replacement |
Please note that “infinity” on the multimeter screen is often displayed as the number 1 in the most significant digit or the OL symbol. This means that no current passes through the part. A healthy starting winding circuit in a static state (for a posistor) is characterized by the presence of resistance.
Replacement and installation of a new component
If diagnostics confirm a malfunction, you must purchase an analogue. Look for markings on the body of the old relay, for example PTC Relay or a specific model number like R600a. Matching current and voltage parameters is critical for safe operation.
Installation is carried out in the reverse order of removal. Push the new relay onto the compressor pins as far as it will go. Make sure it fits snugly and doesn't wobble. Then connect the terminal block of the wires, observing the color markings or photographs taken earlier.
After connecting, secure the protective cover and turn on the refrigerator. If the engine starts the first time and runs quietly, it means repair it was successful. During the first hours of operation, periodically check the temperature in the chamber to ensure the correct cooling cycle.
Frequently asked questions and answers from experts
Is it possible to temporarily start a refrigerator without a relay?
Theoretically, you can start the compressor by applying voltage directly to the starting winding, but doing this is strictly not recommended without special knowledge. This may lead to burnt out motor windings or a fire. The relay is a protective mechanism, and its absence is dangerous.
Why does a new relay burn out after a few days?
If replacing the relay does not solve the problem and it fails again, the reason lies in the compressor itself. The motor may have an interturn short circuit or mechanical wear, due to which it consumes increased current when starting, which melts the contacts of the new relay.
How to distinguish a posistor relay from an induction one?
Posistor relays are usually made in the form of a small plastic cube or cylinder with one or more holes for pins. Induction often have a more complex shape with a visible coil inside or winding, as well as a movable core that rattles when shaken.
Is it necessary to discharge freon before replacing the relay?
No, replacing the start relay does not require intervention in the refrigeration circuit. You are working only with the electrical part of the compressor, so evacuation of the system and charging with refrigerant are not required.