Micro wave operates for a few seconds then shuts down, light goes out, but fan continues to work

First I'm not a Kitchen Aid tech.
* The fan is stuck on or the cook cycle has not completed. Either way something is wrong. Try unplug the Micro wave and let it rest for 10 seconds. Power back up and see if the fan still runs. If so then pull the plug. Don't use the M/W
* Check your warranty and call or take it to the service center.
* There are no customer serviced parts in a Micro wave.
*** High Voltage present. High Gauss Magnets present, High voltage storage device hazard present even with power off and disconnected! ***
* Be safe, call for service or get a new unit and dump this one.
Aloha, ukeboy57

The problem is your magnetron tube is leaking RF. The mag tube comes on 2-3 seconds after you hit start, and the RF interfears with the board and shuts it down. Drop the front of the control panel down and watch, it wont happen.. Get a new mag tube put in and you'll be good to go.

follow this steps and fix it. God bless you

1. Main control boardIf your microwave runs for a few seconds and stops, the first thing to check is the main control board to ensure that a shortage has not occurred. If the part is defective then it will need to be replaced to prevent continual shut offs. If this is not the issue, the next step would be to check for a faulty touchpad.
   
2. Touchpad/Control panelIf the control board is not the issue and your microwave continues to shut off after running for only a few seconds, the next thing to check is your touchpad, which is also known as a control panel. Although uncommon for this issue, symptoms are usually that the display and some buttons are working properly; however, when selected some buttons are not functioning. If this is the case the touchpad will need to be replaced.
   

Buy new.

I regularly see (and repair) this light and / or fan failure on model JVM1660SB005 and most any model of over the range microwave.
The problem is on the controller assembly, which I regularly repair very affordably.

At my Web site, you can get details, plus I have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

This light failure often occurs when a bulb goes out and the filament shorts, or when the bulbs are removed or installed without first unplugging the oven from the power line. Either can cause such a failure on the controller.

The lights can can be inoperable or stuck on or stuck in "night light" mode. Sometimes this will similarly affect the fan operation or inside light, too.

For more free DIY and other help & advice, feel free to contact me via my site.

Please include FULL model number*, FCC ID number*, + detailed symptom information. ( * on the tag in cooking cavity or around door frame or control frame or on back)

William E. Miller, AS-EET
http://www.microwavecontrol.com
Microwave Oven Control Panel Repair Nationwide
"Recycling by repairing since 1982"

I regularly see (and repair) this light and / or fan failure on model JVM1660SB005 and most any model of over the range microwave.
The problem is on the controller assembly, which I regularly repair very affordably.

At my Web site, you can get details, plus I have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

This light failure often occurs when a bulb goes out and the filament shorts, or when the bulbs are removed or installed without first unplugging the oven from the power line. Either can cause such a failure on the controller.

The lights can can be inoperable or stuck on or stuck in "night light" mode. Sometimes this will similarly affect the fan operation or inside light, too.

For more free DIY and other help & advice, feel free to contact me via my site.

Please include FULL model number*, FCC ID number*, + detailed symptom information. ( * on the tag in cooking cavity or around door frame or control frame or on back)

William E. Miller, AS-EET
http://www.microwavecontrol.com
Microwave Oven Control Panel Repair Nationwide
"Recycling by repairing since 1982"

magnetron is leaking internally, do not use until magnetron is replaced. the mag creates interference with the control board and resets it

The cost of repairing the micro wave will out cost the replacement value. If its new then use gaurrantee for replacement

Q - The microwave display counts down and the inside light is on,  but nothing is heating and the fan is not running.
A - This most commonly is a bad door switch, other possible problems are a faulty relay or solder joint on the power module, but a bad door switch is most common.
 Q - My microwave is running and sounds like it is working but will not heat up anything.
A - Many thing can do this but, common things are....loose high voltage wire.....poor solder joint on board.....magnetron.....power relay.....
Q - The microwave makes a loud "hum or buzz" noise but will not heat up the food?
A - 9 times out of 10 this is usually this is a bad magnetron, the other time is sometimes a bad high voltage diode. See components section.

If it stops after 22 seconds, that means the controller has detected a problem, usually a problem with the inverter or a bad magnetron.

Due to the lethal voltages used and produced, I do not recommend that an inexperienced person work on these.

You can find an authorized Panasonic servicer here.

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