A sudden stop of the refrigerator compressor is always stressful, because food supplies are at risk. Often the cause of such a malfunction is the failure of the starting relay, which is responsible for starting the engine. In this article, we will look at how to independently, using a conventional multimeter, determine the serviceability of this part and whether it is worth changing it immediately.
Before starting disassembly, you need to understand the operating principle of this unit. Start relay provides voltage to the starting winding of the engine at the moment of start, and then turns it off. If this mechanism jams or burns out, the compressor hums, but does not start, or makes clicking sounds. Important Remember that diagnostics require compliance with safety precautions.
To carry out the work you will need a minimum set of tools: screwdriver, pliers and, most importantly, multimeter (tester). Without a measuring device, it is almost impossible to determine the integrity of internal contacts with high accuracy. A visual inspection often gives only indirect signs of a malfunction, such as a melted body or a burning smell.
The first stage of diagnosis is always a visual inspection. Remove the back cover of the refrigeration unit and get to the compressor. Carefully remove the plastic casing that houses the relay and disconnect it from the motor contacts. Pay attention to the condition of the case: the presence of cracks, blackening or melting immediately indicates that the part requires replacement.
Inside the case you can often see traces of overheating or even charring of the contacts. If you notice that contacts oxidized or coated with carbon deposits, this may be the cause of a poor connection. However, even a perfect appearance does not guarantee the functionality of the internal mechanics or coil. This is why instrumental control is necessary.
Also inspect the pins that go into the compressor. If they have severe carbon deposits or deformation, the new element may quickly fail. Relay different manufacturers (for example, Danfoss, Indesit or Atlant) may have different designs, but the principle of visual defect detection is the same for them. Any physical damage is a stop signal for further operation.
⚠️ Attention: Before starting any work, be sure to disconnect the refrigerator from the power supply! Working with live electrical appliances is deadly. Also let the compressor cool down if it has just been running.
The most reliable way to check is to use a multimeter in resistance measurement mode (Ohm). Switch the device to the appropriate position. If you have a pointer tester, first calibrate it. For a digital model, it is enough to select a measurement limit of 200 Ohms or a testing mode.
Checking the inductance coil is carried out by applying probes to the corresponding contacts. A good coil usually has a resistance of 30 to 60 ohms, although the exact values vary by model. If the device shows one (infinity) or zero, it means that break or short circuit turns have occurred.
Next, we check the contacts. In a thermal relay they must be closed when cold. Place the probes on the input and output contacts. The multimeter should show resistance close to zero. If a characteristic squeak is heard or zeros are lit on the screen, the circuit is intact. The lack of response from the device indicates a breakdown of contact inside the bimetallic plate.
Particular attention should be paid to checking the operation of the mechanism in dynamics, although this requires caution. The thermal relay should open the circuit when heated. Some technicians gently heat the case with a hairdryer to hear the opening click, but this method does not provide accurate digital resistance data. It is better to rely on static measurements.
If your relay has a capacitor (which happens in some starting circuits), it is also worth checking. The capacitor should not be short-circuited. When connecting the tester in ohmmeter mode, the needle should smoothly deflect and return, or the numbers on the screen should quickly increase to infinity. This indicates the ability to accumulate charge.
⚠️ Attention: Do not try to repair a burnt out relay by soldering or stripping the contacts. This device is designed to operate in extreme conditions and after opening the seal is broken, which leads to rapid re-failure.
Why does the relay burn out?
A common cause of relay burnout is not the device itself, but problems with the compressor. If the motor “jams” or has an interturn short circuit, the starting currents increase many times over, which leads to overload and burnout of the starting relay winding. Replacing the relay in this case will only give a temporary effect.
For the convenience of comparing resistance indicators of various elements, use the following table. Remember that the values may vary slightly depending on the ambient temperature and the specific model refrigerator.
| Check element | Normal reading | Fault symptom |
|---|---|---|
| Coil inductance | 30–60 Ohm | 0 Ohm (Short circuit) or ∞ (Open) |
| Thermal contacts | 0–2 Ohm | ∞ (No contact) |
| Capacitor | Charging to ∞ | 0 Ohm (Breakdown) |
| Case insulation | ∞ (Infinity) | Any value (Breakthrough to the body) |
After all measurements have been carried out, it is necessary to analyze the data obtained. If at least one of the key parameters (coil resistance or thermal contact closure) does not meet the standard, the part is considered faulty. Buying a new relay is usually cheaper than calling a technician for diagnostics.
When installing a new part, make sure that it sits tightly on the compressor contacts. Starting device It should not loosen. Also check that the wires do not touch hot parts of the compressor. Correct installation is the key to long service life of the new component.
☑️ Checklist before turning on
Often after replacing the relay, users wonder why the refrigerator did not work right away. Sometimes the compressor takes time to equalize the pressure in the system. If within 5-10 minutes after turning it on, the engine does not start and does not make any extraneous sounds, then the repair was successful.
However, if you hear humming, clicking, but no starting, the problem may be deeper. This may indicate a malfunction of the compressor itself or a lack of freon. In such cases, independent repair can be dangerous and ineffective. Engine The refrigerator is a complex unit that requires specific knowledge.
⚠️ Attention: The characteristics of the starting relays may differ depending on the power of the compressor. When purchasing a new part, be sure to check the markings or catalog number with the old device. Installing an unsuitable relay can lead to burning out the motor windings.
Can a universal relay be used?
There are so-called universal starting relays with three contacts. They are suitable for many models, but their installation requires careful study of the diagram. An error in connecting the contacts (S, R, C) will lead to instant failure of the new element.
In conclusion, it is worth noting that regular maintenance helps to avoid sudden breakdowns. Wipe the back grill from dust, monitor the room temperature and do not overload the refrigerator with food. These simple actions extend the life of the entire unit, including starting equipment.
Self-diagnosis using a multimeter is a skill that will save you money and time. The main thing is to act consistently, do not ignore safety rules and soberly assess your strengths. If you doubt the measurement results, it is better to consult with a specialist.
Is it possible to check the relay without a multimeter?
It is impossible to accurately determine serviceability without a device. You can only judge indirectly by external signs (carbon deposits, smell) or by the method of elimination (replacing it with a known good one). However, “poking” live wires is dangerous and does not provide guarantees.
Why does a new relay burn out after a week?
This is a classic sign of a compressor malfunction. The engine cranks hard, consumes a huge starting current, and the relay burns out from overload. Also, the cause could be a power surge in the network or a defective new part.
What is the difference between PZR and RTP?
PZR (Start-Protective Relay) is the common name. RTP (Thermal Start Relay) is a specific type where thermal protection and the trigger mechanism are combined in one housing. There are also separate circuits where the starting and thermal relays are separate.
How to choose an analogue if the original is not on sale?
You need to look at the power of the compressor (indicated on the nameplate, for example, 1/5 HP, 1/4 HP) and the type of refrigerant. The diameter of the hole for fitting on the compressor pins is also important. It is best to take a relay of the same series or a universal one with a suitable power range.