Situation when a household refrigerator stops cooling, often takes the owner by surprise, and the first suspicious element becomes thermostat. It is this unit that is responsible for turning the compressor on and off depending on the temperature inside the chambers. However, in emergency cases, for example, to check the serviceability of the motor or if there is a need for urgent cooling of products, there may be a need to start the unit directly, bypassing the standard automation.
It is worth understanding that refrigerator without a thermostat will work, but without intelligent control. The compressor will operate continuously or until the circuit is mechanically broken. This method is exclusively a temporary diagnostic measure or an emergency solution for a short period, since the lack of temperature control can lead to freezing of the evaporator and engine failure.
In this material we will analyze in detail the electrical circuit, the algorithm of actions and the risks associated with direct connection of the trigger mechanism. Direct connection of the thermostat contacts closes the compressor power circuit, forcing it to work continuously until it is opened manually. This knowledge is necessary for the master to carry out high-quality diagnostics, but requires strict adherence to safety precautions.
The principle of operation of the thermostat in an electrical circuit
To correctly To exclude an element from the circuit, it is necessary to clearly understand its role. A thermostat (thermostat) is an electromechanical device that opens and closes an electrical circuit when specified temperature thresholds are reached. In the electrical circuit of household refrigerators, it is usually connected in series with the starting relay and the windings of the compressor motor.
Structurally, the device has an input contact, which supplies 220 Volts from the mains, and an output contact, which transmits the current further to starting relay. Inside the housing there is a bellows tube that responds to changes in refrigerant pressure or air temperature, which sets the contacts in motion. When you exclude this node, you actually create an artificial condition of a “perpetually cold chamber”, forcing the system to think that the temperature never drops below normal.
It is important to note that in modern electronically controlled models, the role of a mechanical thermostat is played by thermal sensor (thermistor), which transmits signals to the main control module. In such systems, simply shorting the wires will not start the compressor, since the logical chain is interrupted at the processor level. Our instructions are relevant mainly for mechanically controlled equipment.
⚠️ Attention: Before any manipulations with electrical wiring, be sure to disconnect the refrigerator from the power supply. Working under 220V voltage is deadly to life.
Necessary tools and preparation for work
To carry out the temporary start-up procedure, you will need a minimum set of tools that any home craftsman will have. The quality of insulation and reliability of connections in this case come to the fore, since the currents consumed by the compressor are quite high, especially at the moment of start.
- 🔧 Screwdrivers (phillips and flat) for dismantling panels and removing terminals.
- 🔌 High quality insulating tape or heat shrink tubes.
- ✂️ Pliers and side cutters for working with wires.
- 🔦 Flashlight for illuminating the interior of the engine compartment.
Before starting work, it is necessary to provide access to the rear of the unit. Remove the compressor protective cover, if equipped, and locate the thermostat itself. In most models, it is located inside the refrigerator compartment (temperature control knob) or outside, near the compressor. You will need to get to the terminal block where the wires are connected.
If you plan to leave the refrigerator running for a while rather than just testing the circuit, make sure there is space for ventilation around the compressor. Non-stop operation causes increased heating of the motor housing, and the lack of normal heat exchange can trigger the thermal protection relay.
Step-by-step instructions for connection directly
The process of removing the thermostat from the circuit is technically simple, but requires care. The main task is to connect the input wire (phase) coming from the plug with the output wire going to the compressor start relay, bypassing the switch itself. In the standard circuit, the thermostat has two or three contacts.
If there are two contacts, then everything is very clear: one wire supplies current, the second takes it to the motor. You just need to connect them together. If there are three contacts, then the third is usually responsible for the light bulb or grounding; it should not be touched. Find a pair of contacts that open when you turn the handle, and close them.
☑️ Algorithm of actions when bypassing the thermostat
For a reliable connection, it is best to use a separate piece of wire, twisting it with both ends, and carefully insulate the joint. It is not recommended to simply twist two old wires together, as the contact may be unstable. After connection, plug in the refrigerator. If you hear a characteristic hum and vibration, and the condenser tubes at the back begin to heat up, the circuit is working.
In some cases, you may need to start through a button if the standard starting relay is faulty, but this is a more complex procedure that requires intervention. starting device. As part of the topic of bypassing the thermostat, we are only considering the creation of a continuous power circuit.
Fault diagnosis: table of symptoms
Before deciding on radical measures to start bypassing the automation, you should make sure that the problem really lies in the thermostat. Often the symptoms of a failure of one unit are masked as a failure of another. Below is a table that helps differentiate problems.
| Symptom | Probable cause | Check method |
|---|---|---|
| The refrigerator does not turn on, the lamp is on | The thermostat is faulty or starting relay | Close the thermostat contacts directly |
| The compressor hums, but does not start | Motor jamming or winding breakdown | Measuring winding resistance with a tester |
| The refrigerator turns off after 1-2 minutes | The thermal protection relay is triggered | Check the current consumption and heating of the case |
| The chamber is too cold or warm | Calibration is lost thermostat | Replacing the temperature sensor with a new one |
If, after closing the contacts, the refrigerator started and began to cool, it means thermostat really out of order. However, this does not mean that the system can be left as is. Lack of temperature control will lead to the evaporator becoming covered with a coat of ice, and the compressor will wear out.
It is also worth checking the condition of the wiring. Old wires may have dried out and cracked. If you find damage to the insulation, it must be repaired before connecting the unit to the network. Ignoring this rule can lead to a short circuit and fire.
Risks and limitations of operation without a thermostat
Operating a refrigerator in constant operation mode carries serious risks. The first and most obvious is compressor overheating. The engine is designed for cyclic operation: turned on, cooled the chamber, turned off, cooled down. When working without a break, the oil in the crankcase may begin to coke, and the rubbing parts may wear out at a catastrophic rate.
The second risk is associated with the formation of ice. Without shutdowns, the moisture contained in the air inside the chambers will constantly condense and freeze on the evaporator. In systems No Frost this will block the fan and interfere with air circulation, and in drip systems - the formation of a giant ice block that will damage shelves and products.
⚠️ Attention: Prolonged operation without a thermostat can lead to water hammer. The liquid refrigerant, without having time to evaporate, can enter the compressor cylinder, which is fatal for the piston group.
In addition, electricity consumption will increase significantly. The refrigerator will have light on 24 hours a day, which will have a noticeable impact on utility bills. Therefore, this mode is only permissible while waiting for a new spare part or as a temporary measure for several hours.
What happens if you forget the refrigerator in this mode for a week?
With a high degree of probability, either the compressor windings will break due to overheating, or a complete failure of the defrost system (in No Frost models), which will require expensive repairs of the entire cooling system.
Alternative methods of temporary cooling
If the thermostat is burned out, and you don’t have a new one at hand, and there is no time to wait for delivery, you can consider other options. For example, the use of external timer relays. You can buy a household timer from electrical goods that will plug the refrigerator into the outlet on a cycle, for example, 20 minutes of work and 40 minutes of rest.
This method is safer for the motor, as it gives it time to cool down, although it is less accurate than a standard thermostat. The cycle settings depend on the ambient temperature in the room and the load on the cameras. In winter, pauses can be made longer, in summer - shorter.
Another option is manual control. You can turn the unit on and off from the outlet yourself, based on the temperature in the chamber. Of course, this is inconvenient, especially at night, but it will allow you to save food until a technician arrives or buy a spare part without the risk of burning out the compressor.
Completing work and restoring normal operation
As soon as you have the opportunity to install new thermostat, temporary jumper must be removed. The process of installing a new device is usually the reverse of the removal process. It is important to choose a model with similar parameters, especially if your refrigerator has specific requirements, for example, the presence of a contact for a signal light.
When installing a new thermostat, make sure that the capillary tube (sensing element) is correctly laid in the seat and has no kinks. Inaccurate installation can lead to the new device also not working correctly or quickly failing.
After replacement, be sure to check the tightness of the system if you have worked with the tubes, and check several on-off cycles. A normal mode is considered in which the refrigerator operates for about 30-40% of the total time of the day, maintaining the set temperature.
Remember that modern refrigeration unit is a complex system where all elements are interconnected. Intervention in the electrical circuit must be justified. If you are not confident in your abilities, it is better to entrust diagnostics and repairs to professionals to avoid more serious damage.
Is it possible to leave a jumper instead of a thermostat on a permanent basis?
It is strictly not recommended. This will lead to continuous operation of the compressor, its overheating, freezing of the chambers and a sharp increase in energy consumption. The engine life will be reduced significantly.
Why does the refrigerator hum, but does not start after closing the contacts?
Most likely, the problem is not in the thermostat, but in the start relay or the compressor itself (jamming). A break in the engine starting winding is also possible.
Which thermostat is better: imported or domestic?
Both options have a right to exist. Imported ones (for example, Danfoss, K thermostat) are often considered more durable, but high-quality domestic analogues (TAM) also reliably serve for years with the right selection.
Is it necessary to defrost the refrigerator before replacing the thermostat?
Yes, it is advisable to completely defrost the unit before starting work to avoid moisture getting on the electrical contacts and to ensure convenient access to nodes.