Top 20 LG LMV1813ST Microwave Oven Questions & Answers

F4 means sensor open, You have to check the Humidity sensor.
If you wish to get some details; visit the site linked here. Pull up older posts.

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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.
The problem is on the controller assembly, which I regularly repair. Details are here.

I also have a video available showing how to remove a typical over the range control panel assembly in under 5 minutes.

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If the control panel lights up intermittently, then you either have a loose connection somewhere near the panel, or a failing component on the circuit board itself.

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The fuse can be replaced, but the underlying issue should still be investigated and resolved. Otherwise the new fuse will blow also.
If the microwave is not working the thermal fuse may have blown.
When a microwave stops working the problem is usually the line fuse or within the high voltage circuit; either the high voltage capacitor, diode, transformer or magnetron.

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The circuit breakers may both be functioning properly. What might be happening is that both circuits have other current drawing appliances on them. The circuit breakers react to the sum of all of the currents drawn by all of the devices on that circuit. So, if you have a 15 amp microwave and an 8 amp refrigerator on the same circuit, you would overload a 20 amp circuit by 3 amps.

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What is it that you are losing ? You can set the power level by using the marked touchpads on the touchpanel, much like setting the volume on a TV. If you do not change the power setting and it is taking a long time to heat things or intermittently fails to, that is usually a sign that the Magnetron has reached its use by date and needs to be replaced. Not always an economical proposition unfortunately as spare parts are often exorbitantly priced.
Before removing the cover of the oven in attempt to carry out any maintenance such as replacing the Oven cavity lamp, make sure the oven is disconnected from the power point ! The voltages in a microwave oven ARE LETHAL !

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turntable drive may be fouling on cabinet.
Take out the table and see if it is still slow. To centre the drive- take the panel off the bottom, you may have to cut the metal the first time

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First, check your users manual for proper programming functions. Then either return the oven to the dealer for a replacement, if their policy allows it or contact a factory authorized dealer to service it under the warranty policy.

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The outer cover will have to be removed to gain access.

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I would contact an LG service department and order one.

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take cover off there are plastic catches who could have wear and tare

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try this manual i found

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Disconnect power and wipe down with vinegar and baking soda solution. Then plug in and heat the same solution for a minute or two. This should take that smell away.

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