LG Microwave Has a Burn Mark on the Side and Is Not Heating

Use only checks that match the exact appliance or system and its official guide.

1. Check 1

   Stop the microwave immediately if there is smoke, a strong or persistent burning smell, visible arcing or sparking, a hot or damaged cord or outlet, a damaged door, or a burn mark inside the cooking cavity. Once it is safe, disconnect power without touching wet or damaged electrical parts; do not run another heating cycle.

   Expected result: The mark is inside the cavity or near the door/seal, or the smell, smoke, spark, heat or damage continues; alternatively, there is only a superficial accessible mark with none of those warnings.

   Next step: For any cavity, door, smoke, odor, spark or electrical damage, leave the microwave off and arrange qualified LG or microwave service. Do not clean through the door gap, open the cabinet or test it with water.

   Why this matters

   Why: LG says a damaged cavity can arc or spark and requires repair, and that continued strong burning smell or smoke requires immediate stop-use, unplugging and service. A visible cavity burn cannot be cleared by guessing that it is food residue.

2. Check 2

   With power disconnected and the unit cool, identify the mark without removing covers: note whether it is food or grease on the interior surface, a chipped or blistered cavity coating, rust or a hole, a damaged waveguide-cover area, a mark on the exterior cabinet, or residue on the door and frame. Do not scrape, sand, paint, tape or patch a cavity or waveguide area.

   Expected result: The residue wipes away from an intact surface, or the coating, wall, rack support, door, seal or frame is scorched, cracked, loose, rusted or perforated.

   Next step: If the surface or door is damaged, photograph the area and provide the complete model number to service. If it is only accessible food residue and all safety surfaces are intact, clean only as the exact LG manual permits; do not power the unit until the residue and condition are verified.

   Why this matters

   Why: LG lists food buildup, unsuitable cookware, rack contact and cavity damage as different arcing conditions. A mark that changes the cavity surface or door sealing area is a service condition, not a cosmetic repair.

3. Check 3

   If there is no cavity or door damage, no smoke or persistent odor, and the exact model manual allows user cleaning, check only the removable glass tray, rotating ring, visible food spills and any supplied rack. Use microwave-safe cookware only; do not use metal, metallic trim or wire ties, and do not operate the oven empty.

   Expected result: Food residue or an incorrectly seated removable tray/rack is present, or the interior and accessories are clean, intact and correctly seated.

   Next step: Correct only the accessible residue, cookware or removable accessory position documented for the model. If the mark remains, the cavity is damaged, or the unit still smells, sparks or fails to heat, stop and request service instead of retrying.

   Why this matters

   Why: LG says food particles can carbonize and spark, metallic cookware can spark, an improperly installed rack can touch the cavity wall, and an empty oven can burn or scorch the cavity. These checks explain an external cause only when the cavity itself is undamaged.

4. Check 4

   Separate a heating complaint from a power or control complaint by checking the display, outlet and circuit from outside. Confirm the cord is in a wall outlet rather than an extension cord or surge protector, and check a GFCI or breaker only once if there is no heat, smoke, odor or visible electrical damage.

   Expected result: The display is dead or the outlet has no power, or the microwave powers up but does not heat and the outlet remains stable.

   Next step: If the outlet or circuit is the problem, use a qualified electrician when a reset does not hold. If the microwave powers up but does not heat, or a breaker trips again, leave it off and arrange LG or qualified microwave service; do not open the cabinet.

   Why this matters

   Why: LG says no power can come from the outlet connection, GFCI, breaker or a unit fault. Stable power with no heating is a microwave service issue; it does not identify a magnetron, diode, fuse or control-board failure for owner replacement.

5. Check 5

   If and only if the cavity, door, cord, outlet and accessories are confirmed intact and there is no burning warning, use the exact LG model support page for a normal heating check. LG’s general guidance uses a cup of water to assess reheating, but do not perform that powered test when the assigned burn mark may be cavity damage.

   Expected result: The model-supported check heats the water normally, or the water remains cold, the mark reappears, sparking occurs, or an odor or smoke returns.

   Next step: If the safe model check fails or any warning returns, unplug or isolate power only when safe and arrange service with the model number and photos. Do not repeat the test, bypass interlocks or attempt high-voltage repair.

   Why this matters

   Why: Water heating can distinguish a normal heating result from a no-heat symptom only on an otherwise undamaged unit. A return of the burn, spark, odor or smoke overrides the test and requires stop-use; it is not evidence for a DIY internal part replacement.