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Microwave starts running as soon as the door is shut, but not cooking?

Microwave starts running as soon as the door is shut, but not cooking?

My microwave runs everytime I close the door. It doesn't cook anything, just runs the turntable and the light. It seems to be registering an error with the door, but not sure how to fix

Asked by: Guest | Views: 217
Total answers/comments: 6
Guest [Entry]

"Cause 1

Diode

The diode converts the A/C power output of the transformer to D/C, doubling the voltage to nearly 5,000 volts. This high voltage powers the magnetron to heat the food. If the diode burns out, the magnetron won’t receive enough voltage to operate, preventing the microwave from heating. When the diode fails, it is often visibly burned out. Inspect the diode and if the diode is burned out, replace it. If inspecting the diode proves inconclusive, test it with a multimeter that uses a 9-volt battery or put a 9-volt battery in series with the diode. When the leads are reversed, the diode should only have continuity in one direction. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the diode.)

Cause 2

Door Switch

Most microwaves have three or four door switches. When the microwave door closes, the door switches actuate in sequence to ensure that the door is closed properly. If any of the door switches fails, the microwave will not start or heat. To determine if any of the door switches are defective, use a multimeter to test each of the switches for continuity. If any of the door switches does not have continuity, replace it. (Caution: The microwave oven can store thousands of volts of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace a door switch.)

Cause 3

Magnetron

The magnetron uses high voltage, high current DC power to generate the microwave frequency that cooks the food. If the magnetron burns out, the microwave won’t heat. The magnetron is not repairable—if the magnetron is burned out, you must replace it. (Warning: The microwave oven can store a lethal amount of electricity in its high voltage capacitor, even after the microwave oven has been unplugged. Due to the high running voltage and the potential for electric shock, it is extremely dangerous to replace the electronic components in a microwave. Only a licensed technician should replace the magnetron.)"
Guest [Entry]

This just happened to me. In my case, all I had to do was clean the door switch pieces on the door and inside and that allowed me to begin cooking again as normal. I'll keep an eye on it though because this is worrisome. This microwave isn't even 2 years old yet!
Guest [Entry]

I replaced the door switch mounting block that was worn out and when I got it back together the same thing was happening to me. The cooling fan ran whenever I shut the door. Come to find out I didn't notice that the little lever that operates the bottom switch wasn't on the new part. So once I took it off the old block and put it on the new block problem solved
Guest [Entry]

I was actually looking for an answer here. My microwave (same model) after 2 years runs as soon as I close the door (intermittently). It’s not actually activating the magnetron as nothing warms up. No table movement, no heat, and no counter/timing display. The microwave still lights the inside lamp, and the fan still blows. I have seen this over the last 20 or so years and normally this problem is due to the door switch microwaves (easy fix…unplug the system from line voltage first and ohm out the switch when it closes = if it doesn’t change resistance {open/closed} it’s always closed). I can’t duplicate the problem using a plastic device to test this theory when on, with the microswitch closed physically by the plastic pot. turner stick and system on. Looked like possible magnetic switch on face of door, or where these “bumps” hit on the inside of the microwave front plate (I used a magnet thinking it used a “reed switch”) but that had no effect. Hope I added some simple troubleshooting here but would like it if someone else had a better response for my problem. Thanks to all, that’s how we help each other !!
Guest [Entry]

"I had the same problem a few mins ago. Right after a major thunderstorm, even though microwave was unplugged. This is how I fixed it.

Unplug the plug from the electric outlet with caution, and very quickly plug it back in. It resets something inside the microwave with the sudden quick surge when u plug it back in very quickly.

Try it again - as I did -if it doesn't fix it completely the first time.

Exercise caution. Wear slippers, avoid contact with water."
Guest [Entry]

Hey guys, i have been having the same issue with my microwave, where the the fan turns on as soon as the door shots. I read all the comments on what might be a potential cause of the problem and still couldn’t quite understand the problem. i found a potential fix while messing with mine, i have a standard 1200W cu whirlpool microwave, if you hold the cancel button for 3 secs it should lock the microwave even if the microwave door is open. And what that does is it prevents the microwave from being functional. you can close the door after you lock the micro wave and then hold for 3 secs to unlock. And that should stop the fan from turning on automatically after the the door shots. BUT my micro wave still couldn’t heat up my food after that trouble shooting. Try this out and let us know if yours heats up your food!! Thanks!!