What to do if the microwave works but does not warm up

Sometimes we are surprised to find out that the microwave does not warm up/defrost the food. Everything works, lights on, spinning, but the food remains cold. What to do? In order not to carry it to repair, you can try to eliminate the breakdown with your own hands.

Why problems can arise

As usual, the causes of breakdowns of the microwave oven lie in non-compliance with the rules of operation. This accounts for most of the problems with household appliances and this case is not an exception. Most often malfunctions begin after:

Cheap ovens can often break down. They are made in such a way that they are less likely to be repaired and more likely to be bought new. And the last obvious reason is wear and tear on parts. If your furnace has been in service for a decent number of years, most likely the parts have simply exhausted their working life. As you can see, there are not many technical reasons. Mostly it is the erroneous actions of “users”. The result – the microwave does not heat or does not turn on at all.

Microwave device

To make it easier to repair the microwave oven, let’s familiarize ourselves at least in general terms with its device. Most of all we are interested in its “insides”.

Produces microwaves magnetron. It is connected to the chamber with a rectangular waveguide. In some models, the waveguide covers a piece of mica (a gray-brown material similar to metal), in others – a plastic cover. The magnetron is powered by a transformer, capacitor and diode. There is often a high-voltage fuse in the power supply circuit, which protects the transformer from overloading.

A fan is used to cool the magnetron. Warm air from the magnetron through a duct also enters the working chamber, which accelerates the heating of food. From the chamber, steam and excess air are removed through special holes that do not allow radiation.

To prevent the microwave oven from working with a loose door, locking microswitches are placed. As long as their buttons are not pressed (the door is not closed), no power is supplied. When the door is opened, the power circuit is broken instantly. One of the reasons why a microwave oven will not turn on is because these small parts are broken or sticking.

The number of micro switches depends on the model. They can be from 2 to 5 pieces. Some manufacturers use them in the circuits of the start button and power control. So one of the reasons why the microwave does not heat can be damage to the microswitch in the power control circuit.

For lighting in the chamber, an incandescent lamp is installed. Most often it is located inside the duct.

The modes of operation 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 can have variants: there can be usual buttons, which select the mode, or there can be a touch panel. If the trouble happened with the control, it is better not to get into electronics without knowledge and skills. The only thing you can check is how well the conductors hold. Everything else – only if you have the appropriate experience.

Microwave does not warm up: simple causes

There are situations when you put food to heat up, everything seems to work, but even after a long period of time, the temperature of the food is insufficient or it is cold. The reason that the microwave does not warm up can be both a serious breakdown, and easily removable reasons. Let’s start with the easy one:

All other causes are more serious and must be dealt with separately.

More serious causes

In this section, let’s look at the damage that can cause a microwave to not heat, even though everything is spinning/lighting. To restore functionality is more difficult than in the previous paragraph, but not so much that you can not cope with your own hands.

Fuse

Sometimes the microwave does not heat because of a faulty fuse in the power supply circuit of the magnetron. It is not found in all models, but it can be the cause of the magnetron not working. This fuse is sometimes installed open, but more often in a protective cover (see not photo), as it stands in the high-voltage circuit.

It consists of a glass bulb with metal caps around the edges. Inside is a spring-loaded wire soldered at one edge to the contact of the cap. Unlike conventional fuses, in this one the wire does not burn out. With prolonged operation, the solder heats up and softens, the elastic force of the spring spreads the contacts.

If the fuse does not ring and a break in the circuit is visually visible, there are two ways to solve the problem – replace it or restore soldering. To restore the high-voltage fuse, it is necessary to carefully remove the metal cap from the side on which the wire has been soldered off, solder it back in place. Put the cap back in place and check the operation – heats or not.

Problems with the magnetron

There are several damages related to the magnetron. Let’s start again with the simplest one – weak contacts. On the terminals (on the connector) of the magnetron come wires from the filament winding of the transformer. They should be removed with difficulty. It is possible that the contact has deteriorated due to heat. It can be improved by crimping the contacts with pliers.

Sometimes the microwave does not heat because of damage to the cap of the magnetron antenna. If the cap is simply blackened or there is a solidified drop of metal on it, but there are no extra holes, it is necessary to clean everything to a clean metal, the surface to make flat. It is necessary to work with fine sandpaper. Achieve the maximum effect – everything should be even/smooth, preferably to a mirror shine. But do not wipe the metal to holes. When the work is finished, 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 is not damaged and in the middle of the vacuum is preserved. To do this, carefully remove the cap and inspect what is underneath. If the metal is intact, you can simply replace the cap. If not – you will have to replace the magnetron, but you should think about the feasibility of such repairs – the price of this part is high, it may be worth just buying a new oven.

How to replace the magnetron cap? It is not easy to find it on sale – it costs pennies, it is not profitable to sell. There is an option – to grind on a lathe. If this method does not suit you, you can make a cap from an old electrolytic capacitor of suitable size.

We select an element of suitable diameter, cut off the necessary piece of the case, carefully drill a hole in the center. Coincidence in all dimensions should be perfect. After that, we clean the body with the finest sandpaper and polish: the quality of the microwave depends on the conductivity of the cap. Ready cap put in place, check the work.

If you still decide to replace the magnetron, take it with you to the store. The new one should match the output power, the antenna should be the same length, the mounting tabs should also be located there and on the same side. Only then can it be installed in place of the old one.

Problems with the mica plate

On the chamber side, the output of the waveguide is covered by a mica plate. Sometimes the microwave does not heat due to the fact that it has formed fouling and the waves simply can not overcome this obstacle. Also because of this damage, sparks and something similar to lightning or even fire can appear during operation.

In this case, we 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 scrub everything. Thoroughly remove the dust (you can vacuum clean), put the plate back 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, the stores know about mica for microwaves. You put the new plate in place (you may need to drill holes for fasteners) and check. If the microwave didn’t warm the food because of it, everything should work.

Capacitor burned out or diode defective

If the microwave stopped heating – everything turns on, buzzes, spins, but the food stays cold, it may be the capacitor. Take a tester and check it. Set it in the resistance measurement mode.

If the measurement shows a break – it is not working, if it shows a small resistance – it is also replaced, because it is broken. Only if the arrow “flies” to infinity when touching the capacitor – it is in normal condition.

Checking a high-voltage diode is not an easy task, so most often it is simply replaced. It does not cost so much that it is a problem. Naturally, the parameters of the new spare part must match.

The reasons that the microwave does not heat can be many more – it is necessary to consistently check all the elements and conductors. But since manufacturers have different schemes, it is necessary to understand on the spot. Basically, in the process of finding out all the above described breakdowns, you will see if the wire is soldered / frayed, soldering came off, etc. All these nuances are monitored and eliminated. Ideally, it should work.