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Sometimes, having put food to warm up / defrost, we are surprised to learn that the microwave does not heat. Everything works, glows, spins, but the food remains cold. What to do? In order not to carry it in for repair, you can try to fix the breakdown with your own hands.
Why Problems Might Occur
As usual, the causes of microwave oven breakdowns lie in non-compliance with the operating rules. This accounts for most of the problems with household appliances and this case is no exception. Most often, problems begin after:
- There is a metal object in the chamber during reheating/defrosting/cooking. Most often it is a spoon or fork, which is in a dish with food. At the same time, the microwave begins to spark, and then it starts to act up – it sparks, does not heat the food.
- Another fairly common situation that often leads to breakdowns is heating in a sealed container that is not intended for this. When a certain temperature is reached, the dishes explode, food scatters around the chamber, clogging the details of the oven. It is rare that such an incident remains without consequences (washing the camera does not count).
The arrangement of parts can be like this - Also, users often forget that you can not turn on the microwave oven empty. In this mode, it starts to spark even more than if there is a metal object in it. The result is problems with the magnetron and the microwave does not heat.
Cheap stoves can often break down. They are made in such a way that they are less repaired, and more often bought new ones. And the last obvious reason is the wear of parts. If your oven has been serving for a decent number of years, most likely the parts have simply exhausted their working life. As you can see, there are not so many technical reasons. Basically, these are erroneous actions of “users”. The result is that the microwave does not heat or does not turn on at all.
Microwave device
To make it easier to repair a microwave oven, let’s get acquainted at least in general terms with its device. Most of all we are interested in its “insides”.
The magnetron produces microwaves. It is connected to the camera by a rectangular waveguide. In some models, the waveguide is covered with a piece of mica (a gray-brown material that looks like metal), in others – with a plastic cover. The magnetron is powered by a transformer, a capacitor and a diode. There is often a high-voltage fuse in the power circuit that protects the transformer from overload.
A fan is used to cool the magnetron. Warm air from the magnetron through the air duct also enters the working chamber, which accelerates the heating of food. Steam and excess air are removed from the chamber through special openings that do not allow radiation to pass through.
To prevent the microwave oven from working with a loosely closed door, blocking microswitches are installed. Until their buttons are pressed (the doors are not closed), power is not supplied. When you open the door, the power circuit breaks instantly. One of the reasons that the microwave oven does not turn on is the breakage or sticking of these small parts.
The number of microswitches depends on the model. They can be from 2 to 5 pieces. Some manufacturers also use them in the start button and power control circuits. So one of the reasons why the microwave does not heat up may be damage to the microswitch in the power control circuit.
An incandescent lamp is installed in the chamber for illumination. Most often it is located inside the duct.
Operating modes are set from the control panel. It may contain electromechanical switches, or it may be made on the basis of a microprocessor. Digital control again may have options: there may be ordinary buttons that select the mode, or there may be a touch panel. If trouble happened with the management, it is better not to go into electronics without knowledge and skills. The only thing that can be checked is how well the conductors are holding. Everything else – only if you have the appropriate experience.
The microwave does not heat: simple reasons
There are situations when you put food to warm up, everything seems to work, but even after a long period of time, the temperature of the food is insufficient or it is completely cold. The reason for the fact that the microwave does not heat can be both a serious breakdown and easily fixable reasons. Let’s start easy:
- The microwave oven may not heat well due to low mains voltage. For normal operation of the magnetron, 220 V is required. If the voltage is lower, it will work, but the temperature will rise very slowly. The situation is treated by installing a stabilizer. Naturally, it is better at the entrance to a house or apartment, but you can put a small stabilizer only on this equipment.
If the microwave does not heat, you will have to repair it. - If the input voltage is 220 V, but the oven is turned on in line with other powerful appliances, a voltage drop may occur during simultaneous operation, which also leads to the fact that the microwave does not heat food well. It is quite simple to avoid this situation – you need to switch some of the devices to other groups (to sockets connected to another branch).
- There is no contact in the socket or the cord is damaged. It is easy to check the contact – you can plug it into another outlet. The power cord is first inspected visually. If there is no visible damage, it is advisable to ring it. To make sure that he is not to blame without a dial tone, you can bend it in different places during the operation of the microwave. If this does not affect the operation, then the cord is intact.
All other causes are more serious and should be dealt with separately.
More serious reasons
In this section, we will consider damage that can lead to the fact that the microwave does not heat, although everything is spinning / glowing. To restore performance is more difficult than in the previous paragraph, but not so much that it was impossible to do it yourself.
Fuse
Sometimes the microwave does not heat up due to a faulty fuse in the magnetron power circuit. It is not available in all models, but it can cause the magnetron not to work. This fuse is sometimes installed openly, but most often in a protective casing (see not photo), as it is in a high-voltage circuit.
It consists of a glass flask with metal caps installed along the edges. Inside is a spring-loaded wire soldered at one end to the cap contact. Unlike conventional fuses, this wire does not burn out. During prolonged operation, the solder warms up and softens, the spring force separates the contacts.
If the fuse does not ring and an open circuit is visually visible, there are two ways to solve the problem – replace it or re-solder. To restore the high-voltage fuse, you must carefully remove the metal cap from the side from which the wire was unsoldered, solder it in place. Return the cap to its place and check the work – it heats up or not.
Problems with the magnetron
There are several damages associated with the magnetron. Let’s start again with the simplest – weak contacts. Wires from the filament winding of the transformer come to the terminals (to the connector) of the magnetron. They must be removed with difficulty. It is possible that the contact has deteriorated from heating. It can be improved by additionally crimping the contacts with pliers.
Sometimes the microwave does not heat up due to damage to the cap of the magnetron antenna. If the cap just turned black or there is a frozen drop of metal on it, but there are no extra holes, you need to clean everything to bare metal, make the surface even. You need to work with fine sandpaper. We achieve the maximum effect – everything should be even / smooth, preferably to a mirror shine. But do not wipe the metal to the holes. Upon completion of work, carefully remove all dust. The best way to do this is with a vacuum cleaner.
If the cap is melted – as in the photo above, you need to make sure that the magnetron itself was not damaged and that a vacuum was preserved in the middle. To do this, carefully remove the cap and inspect what is under it. If the metal is intact, it will be possible to simply replace the cap. If not, you will have to change the magnetron, but at the same time you need to think about the feasibility of such a repair – the price of this spare part is high, maybe you should just buy a new furnace.
How to replace the magnetron cap? It is very difficult to find it on sale – it costs a penny, it is unprofitable to sell. There is an option – to grind on a lathe. If this method does not suit you, you can make a suitable size from an old electrolytic capacitor.
We select an element of a suitable diameter, cut off the desired piece of the body, carefully drill a hole in the center. All sizes must match perfectly. After that, we clean the case with the finest sandpaper and polish it: the quality of the microwave oven depends on the conductivity of the cap. We put the finished cap in place, check the work.
If you still decide to replace the magnetron, then take it with you to the store. The new one must match in output power, the antenna must be the same length, the mounting protrusions must also be located in the same place and on the same side. Only then can it be installed in place of the old one.
Problems with mica plate
From the side of the chamber, the waveguide exit is covered with a mica plate. Sometimes the microwave does not heat up due to the fact that soot has formed in it and the waves simply cannot overcome this obstacle. Also, due to such damage, sparks and something like lightning or even a fire can appear during operation.
In this case, remove the plate by unscrewing the screws (from two to eight pieces). If there are no irreparable changes (no hole), you can try to clean the blackened place. We take fine sandpaper and carefully clean everything. We carefully remove the dust (you can use a vacuum cleaner), put the plate in place. To be sure that everything works, you can turn it upside down.
If there is a hole in the plate, it is better to replace it. This spare part is on sale, in stores they know about mica for microwaves. Install the new plate in place (you may need to drill holes for fasteners) and check. If the microwave did not heat the food because of this, everything should work.
Blown capacitor or faulty diode
If the microwave stops heating, everything turns on, buzzes, spins, but the food remains cold, it may be the condenser. We take a tester and check it. Set it to resistance measurement mode.
If during measurement it shows a break – it is inoperative, if it shows little resistance – it is also under replacement, since it is broken. Only if, when touching the capacitor, the arrow “flies” to infinity – it is in a normal state.
Checking a high-voltage diode is not an easy task, because most often it is simply replaced. It doesn’t cost that much to be a problem. Naturally, the parameters of the new spare part must match. There can be many more reasons that the microwave does not heat up – you need to consistently check all the elements and conductors. But since the schemes of manufacturers are different, you need to figure it out on the spot. In principle, in the process of finding out all the breakdowns described above, you will see if the wire is soldered / frayed, the soldering has moved away, etc. All these nuances are tracked and eliminated. In theory, it should work.