Question about Microwave Ovens

1 Answer

Fuse blows. Drawing too much current ?cause.

Not my machine. Was told it just quit. Found a blown fuse. Had no replacement so I used a thin copper wire. With nothing in the oven sounded like it was running. As I watched the fuse became red hot. After 10 seconds before it blew the breaker tripped on the main board. Several tries with same result. Checked the magnetron, transformer, turntable motor and fan. The first 2 gave identical ohm readings as 2 other used units I had on hand. The motors function normally. No shorts detected. I dont know how to check the capacitors

Posted by on

  • Thandanani Nov 21, 2008

    Hi FixYaY, There's no point at this stage in getting a proper fuse. I would need a new one every time I pressed 'start'!

    When I connected the power everything seemed to be working. The display lit up, the machine responded to commands for time settings and nothing blew. When I pressed 'start' the machine started to hum like a normal microwave. I had presumed it was working from the sound it made. Within 5-10 seconds of pressing 'start' the fuse got red hot and the circuit breaker on the main board kicked out( not the earth leakage) and that breaker is rated at 20 amps!

    I had given up on the machine until I got your message tonight and seem to have now misplaced my diagram. Hopefully I got the connections between the transformer, magnetron and capacitor right. I tried several 5 sec. bursts but could detect no change in a lump of fat placed in the oven. I noticed the transf. core already warm after that period of time. The primary was burning hot to touch. When I disconnected the HT from the capacitor of course the hum disappeared as well as the heating of the primary but what does that tell me-is there a short in the secondary or is there some other reason?

    Regards, Thandanani.

  • William Miller
    William Miller May 11, 2010

    Please get a proper fuse first.

    Let me be sure I understand...

    Is it trying to run when it should be idle?

    Please clarify this.



1 Answer

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points


    An expert that got 20 achievements.


    An expert that got 10 achievements.


    An expert that got 5 achievements.

  • Microwave Ovens Master
  • 9,086 Answers

Wow, I've never heard of a microwave having a circuit breaker on the main board.

I would suggest that you test the capacitor and the high voltage transformer.

Here are some links you or someone you know can use (in order given) for test help, but read the safety warnings first:

We're happy to help you with free advice and we'd appreciate your thoughtful rating of our answer.

Posted on Nov 21, 2008


1 Suggested Answer

  • 2 Answers

SOURCE: I have freestanding Series 8 dishwasher. Lately during the filling cycle water hammer is occurring. How can this be resolved

a 6ya Repairman can help you resolve that issue over the phone in a minute or two.
Best thing about this new service is that you are never placed on hold and get to talk to real repair professionals here in the US.
click here to Talk to a Repairman (only for users in the US for now) and get all the help you need.

Posted on Jan 02, 2017


Add Your Answer

Uploading: 0%


Complete. Click "Add" to insert your video. Add



Related Questions:

1 Answer

I have a panasonic microwave oven and it just quit do they have reset button or could it be a fuse

If nothing lights up at all then it probably is a blown fuse. Un-plug your microwave and take the screws out of the back and possibly the sides of your microwave and remove the cover. Find where the power cord goes into the back of your unit and follow the black wire of the cord to either a fuse holder or to a circuit board. Your fuse will be in the holder or on the circuit board. Make sure you replace it with the same size fuse as what you take out. The amperage size is stamped on one of the metal collars on the fuse. Hope this helps!

Feb 17, 2015 | Panasonic Microwave Ovens

1 Answer

Turntable, lights and fan inop

sounds like a cross wire, and a short. I'd inspect the socket for the bulbs to ensure that there's no short circuit.

Feb 11, 2008 | Magic Chef CMV1000B Microwave Oven

1 Answer

Fuse blown in the back of Euromaid oven, What can cause this??

Hard to say what blew the fuse, suggest you replace the fuse and if it blows again take it in for service

Jan 30, 2015 | In Microwave Ovens

1 Answer

Microwave Dead

Having 20 year experience fixing microwaves i know that when the fuse goes that if you can't find a melted wire or overheated components on the circuit board that the high voltage capacitor at the back needs to be replaced. Sometimes you have to replace the magnetron too. You can replace the door switches if you like, microswitches are inexpensive but would only be bad if arced inside so bad that you read over 1 ohm.

Nov 25, 2013 | Microwave Ovens

1 Answer

The microwave won't turn on. it is off completely. Just happened last night. Have checked the electric fuses, poked the buttons, but noty on. Stove is ok.

You have to open it up and see if you can find the power fuse, usually a BUSS 15amp Slo Blo that protects the Microwave Tube from drawing too much current and causing a fire. These fuses degrade over time or some get through that are not quite 15 amps and blow.

Dec 19, 2010 | Jenn-Air JMC9158AAS Convection/Microwave...

1 Answer

3 year old OTR microwave left on with nothing in it. now shows no power,board,lights or fan. what do I check first?

You have to open it up and see if you can find the power fuse, usually a BUSS 15amp Slo Blo that protects the Microwave Tube from drawing too much current and causing a fire. These fuses degrade over time or some get through that are not quite 15 amps and blow.

Dec 19, 2010 | Kenmore 69642 Microwave Oven

1 Answer

No power to microwave

There is usually a 125V, 20 AMP line fuse inside the microwave. Its usually mounted at the point where the power cord enters the back of the unit. Unfortunately, you will need to uninstall the oven (if this is an over the range model), UNPLUG it and remove the exterior case to access. The case comes off in various ways depending on manufacture and model. I found this illustration at based on the model number you listed this question under:

The line fuse is listed as item 28 in the drawing. Keep in mind, there are also a couple of thermostats listed that may also cause no power problems if blown.

One is listed as item 29 (part number 8183703) under the same drawing. The other is listed under the "Airflow" section as item 5 (part number 8183697). The humdity sensor can also be a source of problems when it becomes old. If you managed to overheat the oven any time recently, you may want to check these thermostats and sensors to see if they are still good. They should read 0 ohms when measured out of the circuit.

If the line fuse is blown, you can usually purchase a box of fuses at a hardware store for just a little more than what the manufacturer charges for a single fuse. 125V, 20AMP Ceramic Slow Blow fuses are recommended. If you wish to order on line, use the part numbers to search by comparison as the model number you listed this question under may not be available at all the websites I have provided. The parts, however, ARE listed.

If you have any questions, or need additional assistance troubleshooting, please post back and let me know. I hope you find this information helpful.

NOTE: Make sure you take any resistance readings with the microwave UNPLUGGED and the component under test isolated (removed) from the circuit. These ovens can blow a fuse by simply sitting idle. This can occur from any power fluctuations, brown outs, voltage spikes, etc. Or, it could be the symptom of a component that may have failed. If you find the internal fuse blown and replace it, only to have it blow again, you have a more significant problem than a simple blown fuse.

May 22, 2010 | KitchenAid KHMS155LSS 1000 Watts Microwave...

3 Answers


There are two fuses in a microwave oven, and for the non-heating problem the problem is the high voltage fuse, incapsulated between the transfo and the magnetron. This supports up to 5000V and usually rated something like 0.65A/0.7A/0.8A and even 1A.
When you open the capsule, you'll see it sitting there between its two connectors, and you'll notice the filament inside the glace is broken. Buy a new one and your machine will work like a horse.
NOTE: Try to get the same ratings fuse, or else the oven will smoke and smoke the house with it, so be careful.
The other fuse is smaller, and usually ceramic one, which can be found on the PCB, if that goes, you should get no power at all to the machine. If not sure, let a professional do the job, it's safer.

Apr 09, 2010 | Westpoint TV-201 Microwave Oven

3 Answers

Turns on but doesn't heat only a year old LG LRM1260SW 1200 Watts Microwave Oven

I have had the LG model lrm1260sw microwave for 3 years. Recently it quit heating. I found the problem was the soldered grounding lug connection on the power transformer had lost circuit continuity and failed. One of the secondary coils on the power transformer, red wire / bare copper wire, is connected to ground / chassis. I cleaned the lug connection and added a length of wire twisted together with the bare copper coil wire and soldered to the grounding lug. I then grounded the extra added length of wire to another chassis ground point. Make sure the transformer to chassis mounting screws are tight also. Now the microwave oven works like new again.

Feb 27, 2010 | LG LRM1260SW Microwave Oven

Not finding what you are looking for?
Microwave Ovens Logo

Related Topics:

507 people viewed this question

Ask a Question

Usually answered in minutes!

Top Microwave Ovens Experts

William Miller
William Miller

Level 3 Expert

9086 Answers

Donald DCruz
Donald DCruz

Level 3 Expert

17130 Answers


Level 3 Expert

77169 Answers

Are you a Microwave Oven Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides