The answer, before the detail
A Black+Decker BDMW microwave that trips, arcs or smells hot has told you enough to act on. Switch it off and unplug it before anything else. What can then be checked from outside is short: what was in the cavity, the state of the waveguide cover, the outlet it plugs into, and on an over-the-range machine the grease filters. Everything else is a service call. What separates BDMW units here is visible without a tool: a glass turntable, or nothing of the sort on the other build.
What the owner actually sees
- It runs for a moment then takes the circuit out — A start draw the circuit cannot carry, or a fault inside the oven itself.
- Sparks or flashes inside the cavity — Never run it again to see whether it does it twice.
- A burning or electrical smell — Unplug it. A smell like this is not something to reproduce for diagnosis.
- Heat at the wall rather than at the oven — Do not keep using the socket.
- The circuit visibly struggles with it — A standard household branch circuit is 15 A or 20 A at 120 V, and a microwave asks for a large share of one.
- NEAR MISS — arcing that stops when the foil comes out — That is the oven behaving correctly around metal it was never meant to heat.
Most likely first on this family
- Metal in the cavity — foil, trim, a twist tie or a skewer — It ranks first wherever the sparking stops when the offending item comes out. Gold or silver trim on a dish arcs exactly like foil does.
- The waveguide cover is soiled, burnt or damaged — It ranks high because it is the one internal-looking part that is owner-replaceable from inside the cavity, without opening the cabinet.
- The circuit is shared, or the outlet and cord are damaged — It is placed here because it explains tripping without any arcing, which the causes above do not.
- Grease-loaded filters or a blocked vent on an over-the-range machine — It is ranked here because it explains a hot smell with no arcing at all.
- A high-voltage component, the magnetron or the diode — It comes last as the diagnosis of exclusion: tripping with nothing in the cavity, clean cover, sound outlet.
The order that finds it fastest
- Take the oven out of service before diagnosing anything — Arcing, tripping and burning smells are all conditions to act on rather than to reproduce.
- Look for metal, foil or metallic trim — If the arcing goes with the metal, the oven is behaving correctly.
- Look for scorching on the small panel inside — It is replaced from inside the cavity — the cabinet still never comes off.
- Feel the plug and look at the socket — Warmth or discolouration at the wall is an electrician job, not an appliance one.
Power off first
Safety
Never open the cabinet of a microwave oven. The high-voltage capacitor inside can hold a lethal charge long after the machine is unplugged, and nothing behind that cover is an owner part on any model. Unplug the oven before cleaning anything, leave every door interlock exactly as it is, and do not run the oven empty.
When to call a technician
The condition is whether the cause is in the cavity or behind it. Metal, a charred waveguide cover and greasy filters are all in the cavity or on the outside, and all of them are yours. Anything else — a magnetron, a diode, a capacitor, the wiring behind the panel — is a technician job on an oven that stays unplugged until they arrive.
Other faults covered for the BDMW models
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
