Problem: No Heat.
Microwave ovens are found in every house hold. You can either cook or heat up food.  It comes in different sizes and models but all of them have one function, cook and heat. In my home town, especially in winter time, the electricity sometimes causes a lot of problem. Sometimes we lose electricity in the city. When the Electrical Company restores it, the power voltage shoots up to 280 before it is restored to the normal 220 volts. Due to this problem, a lot of electrical and electronic equipment break down in the house and cause them to malfunction.

In this case, the microwave oven either will shut down completely or stop heating up the food. In this article, I will deal with no heat problem. It is very easy to fix but there few important points you have to take into account when working in microwave ovens.

1. Always unplug the microwave oven from the main output.

2. Always, it is very important to discharge the main capacitor in the high tension area. The charge in these capacitors will not kill you but it will scare you to death and the reaction from this charge is you pull your hands away from the equipment and due to that, you will cut yourself in the process. The edges insides the microwave ovens are sharp and therefore carelessness is not an option here. With these important remarks in mind, let us begin the repair.

A. You need to unscrew all the screws on the outside of the microwave oven. Usually on the back and one on the side of it.

B. Once you have done that, you need to take the cover off. Be careful with the sharp edges.

C. Once you open the microwave, you will see the main power board on the top. Usually a small PC board. The control panel, the light, the transformer, the capacitor, the bleeder diode and the magnetron.

D. You need to make sure that the 220 volts are reaching the transformer. So, you unplug the two main power lines usually on the primary side of the transformer, attach the voltmeter there and turn on the machine, there should be 220 AC volts reaching that transformer. Once we do that, the rest should be a walk in the park.

E. Now, it is very important to unplug all the cables connected to the magnetron and the capacitors. Make sure you mark all the cables. I usually use my I- phone camera to take pictures of all the wires in there before I disconnect any cables.

F. It is time now to discharge the capacitors. Either by using two screw drivers or using a light bulb. I always use a 100 watt light bulb to discharge the capacitor.

G. There should be a wire going between the capacitor and the secondary out of the transformer. On the wire, there is usually a .7amp fuse (that fuse is sitting in a white plastic container). Usually when the microwave oven is not heating the food, the fuse will be open. You need to replace that fuse with the same rating otherwise it will cause problems in the microwave oven.

H. Sometimes, on rare occasions, the microwave oven is not heating nor cooking the food and the fuse is not blown. The next step to this problem is the magnetron. This is the main source of heat and you need to replace that.

I. Once you replace the fuse or the magnetron, make sure you put the all the components and the wires back where they belong.

J. Put the cover back on and give it a try. It is very easy and fun to do.
K. One last remark. Sometimes a bad magnetron will cause the fuse to blow. Before replacing that fuse, you need to take out the magnetron out and check the condition of it. (There are usually four screws holding the magnetron to the body of the microwave one).

Happy repair and enjoy heating and cooking your food.


10 years of practical electronics. owner and operator. I service the Bethlehem area in Palestine. I repair Xbox 360 and all play stations and modify their power supplies. also repair lcd and Plasma tv sets, and lcd computer monitors. I have a degree from Bob Jones University in general business and one year degree in Industrial electronics. a intensive course in Media. I also work as a camera and audio man as a free lancer. Also great experience in video editing and installing surround systems for home and movie theaters.

3 comments on “Repairing Microwave Oven With No Heat Problem

  1. warlito baga says:

    Sir, good evening from philippines,,thanks for monthly news,,Godbls with you'r family,,

  2. bogie says:

    Good day Sir,is it possible to test the magnetron if its bad or good? What is the process? Thanks..

  3. Waleed says:

    set your meter to ohm setting and see if there is reading between the two terminals of the magnetron and the body of it. if there is reading there, the magnetron is shorted. the two terminals of the magnetron are suppose to have reading between them..that is normal.

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