The light is dim with the door open or closed running.whats wrong?

If the magnetron is still operating when off, needless to say , its pretty dangerous. The door lock unit usually has at least 3 microswitches to ensure that the door is closed and ready to operate. 1 of the switches is a safety switch which will cause a dead short if the door is forced open or something goes wrong with the door not closing correctly. This will "blow" the internal fuse in the machine. If the magnetron keeps going, its possible one of these switches have failed or there is an electronic fault causing power to the magnetron in the off position although, I would strongly feel this would be unlikely. These machines are made with a lot of safety devices.

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Dimming Microwave Light - Breville Support

brevilleusasupport.com/bmo734xl/dimming-microwave-light/

Apr 10, 2014 - Occasionally, when using power settings that are lower then the normal 100% cooking power, the light inside the microwave cavity may dim.

Door ailment may be a issue or the brackets that hold the switches maybe old and moving. Or wrong switch in wrong spot..

The door switch is adjustable. one or more need adjusting to solve the problem

I'd look for a defective relay or shorted triac on the control panel circuit board. Either could cause this problem.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/david_29ad5d1dd86564b0

It could be a door switch that arced open or closed. It could be a relay that arced open or closed etc

If the cooling fan, light and turntable run continuously when the door is open, but not when it is closed, your secondary interlock (bottom door switch) is shorted (always on).

Even if it's shorted, the actuator button (usually red) will still move up and down when you open and close the door.

It will need a new door switch.

See the service manual here. See our file on door switches here.

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Did you pressed the stop/clear button? or disconnect the micro.. for a couple of hours and try again?

This is probably a bad primary interlock switch (bottom door switch) but there is a chance it's a bad relay or connection on the control board.

If you or someone you know decide to look into it, we have critical information on safety, disassembly and door switches at our site, and our link is at our listing here on FixYa:.

You can find helpful exploded view diagrams and order parts for many brands by entering your full model number here.

There also should be a "mini-manual" hidden inside the unit behind the control panel or hidden on the left side behind the grille, which is very helpful when troubleshooting & testing.

At our Web site, we have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

Door switch or mount trouble is usually caused by slamming the door or by opening the door while it's cooking without hitting the Stop pad first.

There are plastic mounts inside the microwave which hold the door switches and onto which the door latches lock when you close the door.

The screws on these mounts may be loose. If they get too loose, the switches will not be activated properly.

Sometimes it's a broken tab on the switch holder, allowing the switch to rotate just out of position. This tab can be hard to see, since it is under the bottom edge of the switch.

If you only need a switch, you can order a universal type here for $5 postpaid.

If you think the problem is on the control panel, we repair these nationwide by mail for $39.95 postpaid in most cases.

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

The magnatron is shorting, overloading the high voltage transformer. From the picture this looks like an older unit and is probably not worth a magnatron replacement.