How To Repair A Microwave That’s Not Heating

regulating the temperature of the ovenA microwave is one of the most useful kitchen appliances that will save your time and power in heating food. Unfortunately, microwaves sometimes develop problems that need repair that can best be done by a technician considering their complex parts and safety precautions in handling them. Poor heating is a common problem that may be posed by a microwave. If you notice that your food is heating unevenly or not heating at all, then you can identify the problem and have it fixed by an expert. Don’t attempt to fix your heating equipment if you are not are not knowledgeable on its parts. Call a qualified residential appliance technician to visit your home and have your heating unit checked.

 

Identify the basic problem first:

 

Then you may check some common causes for poor heating and how they can be repaired:

 
  1. A defective capacitor
  2. A defective magnetron tube
  3. A defective power diode
  4. A defective thermoprotector

Basic inspection for damage

Before any microwave oven repair work begins, identifying the basic problem should begin. It will usually take a microwave technician less than an hour to inspect the machine’s basic functionality, electrical capacitor and switch efficacy. The basic steps that should be taken before microwave repair begins include:

  • Unplugging the microwave and discharging its capacitor – It is important for everyone using the microwave in your house to understand that the food heating equipment has a capacitor which contains high amounts of voltage that may be very harmful with careless handling of the internal parts even when unplugged. Before the internal parts are opened or touched, it is good to unplug the microwave so that it is discharged.
  • Inspect for any signs of burns – a non-functioning power source may make a microwave not to heat. Inspect the outlet area where you plug in your machine and look out for any signs of burns on cords.
  • Inspect door switches – If the door is not working, it should be replaced. Microwave doors have 3 to 4 switches. If any of the switches are faulty, the machine will not function. When the door is closed, the switches become active and the microwave starts safely. If the microwave’s interior light doesn’t go off after closing the door, then there is a problem with this part.

Other than these signs, a loud or buzzing noise is a clear indication that your microwave is not heating and needs repair.

Common causes for microwave not heating

oven repairman checking the controlsIf your microwave is not heating your food but is just humming or buzzing, then it could be a caused by defective capacitor, diode or magnetron. These problems can be corrected by a microwave service technician with proper licensing.

Below are the common causes of the problem:

A defective capacitor

A capacitor is another vital component of the microwave that stores electricity.

Problem – If the capacitor is faulty, the microwave will just make a buzzing sound and your food will remain cold when you try to heat it.

Repair – A skilled microwave technician can test the device to determine if it’s problematic. A damaged capacitor needs to be replaced for normal function of the microwave. Additionally, if it’s old, it also needs to be replaced. Note that the capacitor has the ability to hold high voltage of electricity that can be very harmful even after the machine has been turned off and unplugged and therefore needs to be discharged first before any testing is done.

Though a capacitor can discharge itself, it’s advisable to discharge it manually. To discharge a capacitor manually, put an insulated handle screw driver between the capacitor’s diode connection and ground.

A defective magnetron tube

A faulty magnetron is another reason why your microwave may not be heating well. A magnetron tube in a microwave is the component that heats up food. The device functions by using high voltage power to produce microwave frequencies that heat up food.

Problem – If this component is faulty, the microwave will just rotate your food while making a buzzing sound but will not heat it up.

Repair – A microwave repairman can inspect if the magnetron or its switch is broken and make a replacement. If the magnetron is old, it will also not work. First, a technician will see if there is any voltage going through the device. If not, power is disconnected from the microwave and the case is unscrewed on the back side. The magnetron is then removed and inspected on its backside where there is a tube. If the tube is burnt, it needs to be replaced. If other parts are not bad and the tube is not burnt, then your repairman will still need to replace it.

A defective power diode

A power diode is an electrical component that functions by allowing current to flow in one direction and blocks it from flowing in the opposite direction. The diode located on the capacitor converts electric power to DC which is delivered to magnetron that converts it to microwave energy.

Problem – A faulty power diode will not heat your microwave even with the humming noise.

Repair – You can call a licensed residential microwave technician to visit your house to test the machine and have the power diode replaced if it is the cause of the problem. To check the diode, power is disconnected and then the diode is unplugged from the capacitor. An ohmmeter is then set to around 50,000 ohms to read the diode. The ohms between both ends of the diode are read. One way should read zero while the other way should read around 50,000 ohms. If the diode is faulty, it will read around zero ohms on either side or nothing in both ways. In most cases, if the diode is faulty, the magnetron tube must also be replaced.

A defective thermoprotector

The thermoprotector is a switch that regulates the flow of heat in a microwave. If the temperatures within the oven exceed the normal, the thermoprotector cuts off power.

Problem – Food may not heat up if the device is faulty.

Repair – A tripped fuse caused by overheating may be the problem. A technician can easily reset the device for normal operation.

repairman examining oven with flashlight

Caution with microwave repair

A microwave will always be a useful household appliance and its failure can be a big frustration in food preparation. Your microwave can pose a fatal electrical shock even after it has been unplugged for several hours. Seek professional service whenever conducting any repair on your microwave unit for your safety. An appliance or microwave technician can safely open the back of your microwave for you if you are not a trained electrical technician.

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