Opening the sealed casing of the refrigerator compressor

Diagnostics and restoration compressor often become the last chance to revive an old or expensive refrigerator when buying a new unit is impractical. Opening sealed casing is a complex operation that requires not only specific tools, but also a deep understanding of the electromechanical system. The main difficulty is that factory assembly assumes the complete absence of the possibility of dismantling without destroying the welded seams.

When deciding on this step, you must be aware: after such a procedure factory tightness will be forever lostand it will only be possible to put the unit back together using welding and vacuuming, which is extremely difficult to do at home. However, if the goal is to determine the nature of the malfunction (jamming of the piston group, combustion of the windings or breakage of the valves), then careful cutting of the housing is the only available diagnostic method.

In this article we will consider all stages of working with metal cap the motor, starting from the selection of tools and ending with an analysis of the internal state of the mechanisms. It is important to understand that safety is paramount, since there may be freon inside under pressure, and the electrical part is under high voltage.

⚠️ Attention: Before starting any work on dismantling the casing, you must make sure that the refrigerant is completely released in a ventilated area. Residual pressure in the system may result in oil splashing or ignition when using an open flame.

Required Tools and Workplace Preparation

To successfully complete the task of dismantling the frame, you will need a set of tools that goes beyond the standard electrician repair kit. The main tool here is Angle grinder (a grinder) with a thin cutting disc for metal, or specialized scissors for cutting metal if the body is made of thin steel. Using a conventional hacksaw for metal is extremely ineffective due to the round shape of the body and the hardness of the material.

In addition to the cutting tool, you will need powerful machinery vice for fixing the unit, a set of open-end wrenches, pliers and, preferably, a blowtorch or a hair dryer for warming up stuck compounds. Don't forget about personal protective equipment: glasses, thick gloves and a respirator are required, since the cutting process generates a lot of metal dust and sparks.

• 🛠️ Angle grinder (grinder) with a 1 mm thick disc or reciprocating saw for metal.
• 🔧 A set of wrenches and screwdrivers for dismantling external elements.
• 🧤 Safety glasses, gloves and a respirator for protection from chips.
• 🔥 A blowtorch or gas torch for heating joints.

The workplace should be well lit and equipped with a reliable support for the compressor. Since the unit has significant weight and a rounded shape, its fixation in a vice through wooden blocks is critical to prevent the tool from slipping.

Dismantling external elements and preparing for cutting

Before you start cutting metal, you must free the compressor from all attached elements. First of all, the starting capacitor is removed start-up protective relay if it is taken out separately. These elements are usually covered with a plastic or metal casing, which is secured with latches or screws.

Carefully disconnect all electrical wires, having previously photographed the connection diagram or sketched it. The contacts may be oxidized, so use contact cleaner spray alcohol to clean them before removing them to avoid damaging the terminals. After removing the relay, you will have access to the three motor terminals located in the insulating block.

⚠️ Attention: Never pull the wires to pull the block out of the housing. Hold only by the plastic base of the terminal block, as the copper legs inside the glass may break off, making further repairs impossible.

The next step is to disconnect the copper tubes. If the compressor has not yet been soldered out of the refrigerator system, you need to cut the suction and discharge tubes as close to the housing as possible with pliers. The remaining stumps will need to be removed or bent so that they do not interfere with the installation of the cutting disc.

Technology for cutting a sealed casing

The most crucial moment is the direct separation of the upper and lower parts of the casing. The factory seam is a double rolled joint, often filled with copper or covered with a thick layer of paint. You need to cut strictly along the joint line, trying not to damage the internal windings electric motor and not to deform the housing itself, so that you can later assemble it back.

The optimal strategy is to make two parallel cuts at a distance of 3-5 mm from each other along the entire circumference of the seam. This will allow you to remove a strip of metal and ensure that the halves are separated, even if the metal at the welding site has different thicknesses. The movements of the grinder should be smooth, without strong pressure, so that the disk does not jam.

If you use a hacksaw or reciprocating saw, the process will take much longer. In this case, it is recommended to make several radial cuts to relieve metal tension, and then carefully, with progressive movements, cut through the perimeter. It is important to ensure that the saw teeth do not jump off and damage varnish coating the wires inside.

Removing the internal mechanical part

After the top cover (cap) is removed, the internal structure will open before you. The motor-compressor is attached to the bottom of the casing by three or four spring hangers. These springs are under tension, and careless handling of them can cause the heavy mechanism to jump out and damage thin tubes or valves.

To remove the unit, you must first unhook the lower hooks of the springs from the housing, and then carefully remove the upper hinges from the engine frame. It is best to do this with an assistant: one person holds the body, and the second works with the springs. The internal block is removed strictly vertically so as not to bend suction tubewhich often passes through the entire mechanism.

• 🔩 Unhook the lower ends of the springs from the bottom of the casing.
• 🔩 Remove the upper spring loops from the motor brackets.
• 🔩 Remove the unit vertically upward, checking the tubes.
• 🔩 Inspect the condition of the oil for metal shavings.

Pay attention to the color and smell of the oil in the crankcase. The presence of a black suspension or metallic sheen (aluminum powder) indicates critical wear of the friction pairs. If the oil smells like burnt insulation, then most likely the problem lies in the interturn short circuit.

Diagnostics of the electric motor and windings

Visual inspection of the windings stator often allows you to immediately identify the cause of the breakdown. Blackened varnish, swelling or obvious breaks in the copper wire indicate thermal destruction of the insulation. However, even if the windings visually look intact, this does not guarantee their serviceability - it is necessary to measure the resistance.

Using a multimeter, ring all three motor terminals. There must be a certain resistance between the common wire and the starting winding, as well as between the common and working windings (usually from 10 to 40 Ohms). The resistance between the starting and working terminals should be the sum of the resistances of each winding relative to the common wire. The absence of readings indicates open circuit, and zero resistance indicates a short circuit.

⚠️ Attention: When checking with a multimeter, be sure to check the resistance between any terminal and the motor housing. The presence of conductivity (multimeter beep) means a breakdown of the insulation on the housing, which makes the operation of the compressor deadly.

It is also worth inspecting the centrifugal switch (if this model has one) and the condition of the bearings. The rotor shaft play should not exceed a few tenths of a millimeter. If the shaft dangles or rotates with difficulty, the mechanical part must be replaced or complexly restored.

Analysis of the piston group and valves

If the electrical part is in order, attention switches to the mechanics. For a detailed inspection, it is necessary to remove the cylinder head by unscrewing two or four screws. Underneath it are discharge and suction valves thin metal plates that play a key role in creating pressure.

A frequent malfunction is the breakage of the valve reed or loss of its elasticity. In this case, the compressor hums, but does not create pressure or pumps extremely weakly. You should also check the cylinder bore and piston for scoring. The presence of deep scratches means that the compressor is “stuck” and its resource is completely exhausted.

• 🔍 Inspect the valve plates for cracks and deformations.
• 🔍 Check the tightness of the cylinder head mounting screws.
• 🔍 Assess the condition of the piston and cylinder (no scuffing).
• 🔍 Make sure that the connecting rod and piston pin are intact.

In some models rotary compressors the design differs from the piston one, and there the main element is the rotor and plate. The diagnostic principle is similar: we look for mechanical damage, scuffing and violation of the geometry of parts.

Assembling and sealing the housing

Assembling an opened compressor is the reverse of disassembly, but with the addition of critical sealing steps. You cannot simply put the lid back on, since the system must be absolutely sealed and evacuated. After installing the internal mechanisms in place, the upper cap is put on the lower part with a slight tension.

To restore the tightness, the seam must be boiled. In domestic conditions, this can be done using gas burner copper-phosphorus solder, if the design allows, or use special sealants for refrigeration systems, although the latter option is less reliable. After sealing the seam, nitrogen pressure testing is required to check for leaks.

The final stage is filling with oil and refrigerant, as well as creating a vacuum in the system using a vacuum pump. Without evacuation, the remaining moisture and air inside will lead to the formation of acids and rapid failure of the compressor.

⚠️ Attention: The use of ordinary air for pressure testing is strictly prohibited due to the moisture content. Use only dry nitrogen under a pressure of no more than 10-15 atmospheres.

If you do not have the skills to work with welding and vacuum pumps, it is better to entrust the assembly to professionals, limiting yourself to diagnostics only. Improper sealing will lead to freon leakage and damage to expensive equipment.

Is it possible to open the compressor without a grinder?

Theoretically, you can use a hacksaw or even punch a hole with a chisel, but this is extremely labor-intensive and risky. A hacksaw can easily damage the windings, while a chisel will deform the housing, making subsequent sealing impossible. A grinder with a thin disk is the most effective and controllable method.

What to do if there are a lot of chips inside the compressor?

The presence of a large amount of metal shavings (especially aluminum) indicates that the piston group is completely destroyed. It is easier to replace such a compressor with a new one, since flushing the refrigerator system from these chips will take more time and money than buying a used unit.

Is it necessary to change the oil after opening?

Yes, definitely. During the opening and diagnostic process, moisture from the air or metal dust could get into the oil. The old oil must be completely drained and the system flushed with a special solvent (for example, freon R11 or R141b) before filling with new compressor oil.

Why does the compressor hum but does not start?

This can be caused by several reasons: jamming of the piston group, faulty start relay or interturn short circuit in the windings. Opening the casing will help to accurately determine the cause: if the shaft turns with difficulty - mechanics, if freely - electrics.

Is it dangerous to open the compressor yourself?

Yes, it is dangerous. Risks include: electric shock (if tested under voltage), injury from flying sparks and disc, and freon or oil fumes from combustion. In addition, incorrect reassembly can lead to an explosion of the casing upon startup.