The short answer
Here is what the symptom means on a Black+Decker microwave: a control that keeps forgetting is being interrupted, and the interruption is usually outside the oven. Moving the oven to its own outlet is the whole test and it costs nothing.
What you actually see
- The display shows a code with the oven otherwise working — A code on a working oven is usually a sensor or a stored state.
- The clock resets whenever the oven runs — A control losing time under load is a supply symptom.
- The display shows partial or flickering digits — Missing segments are a display fault, and the oven usually still works behind it.
- The oven ignores the power level setting — A machine that accepts a level and ignores it separates the input side from the load side.
Causes, ranked for this microwave
- Supply sagging under load — Ranks first because a microwave is a heavy load, and a control on a shared or marginal circuit resets every time the oven starts. This is the entry most often blamed correctly and diagnosed carelessly, so take the extra minute.
- Control left in a stuck state — Second because it costs nothing and it clears a large share of these complaints, so it comes first no matter how the fault looks. Confirm it before moving on, because the entries below read differently once it is ruled out.
- Steam or grease behind the panel — Third because steam from the cavity and grease from cooking work behind a membrane over years and produce intermittent, weather-dependent behaviour. Rule it in or out properly here; a maybe at this position costs an hour further down.
What to check, in order
- First — the outlet and the circuit — Note whether the resets coincide with the oven starting or with another appliance starting nearby.
- Second — a proper power cycle — Unplug the oven for several minutes until the display is completely dark, then restore power and watch the start-up sequence.
Checks an owner can do safely
- Step 1. Power-cycle the oven properly — Unplug it for several minutes until the display is completely dark, then restore power. A quick pull and push does not clear a stored state.
Tools: noneAbout 10 min
- Step 2. Test every button — Press each in turn and record which respond. Grouped failures are a broken track; scattered ones point further back.
Tools: pen and paperAbout 10 min
- Step 3. Look for a lock or a demo mode — Hold each button for several seconds in turn and watch for a lock symbol appearing or clearing.
Tools: noneAbout 10 min
Before you open anything
Safety
Unplug the appliance or switch off its breaker before removing any panel. The high-voltage capacitor in a microwave can hold a lethal charge long after the cord is out, and it is not discharged by waiting. Nothing inside the outer cabinet is an owner-serviceable part, and no fault justifies running the oven with the case open or with a door switch held closed by hand.
When this becomes a service call
Stop and call when the next thing to do meets any of these. A burning smell or visible scorching at the panel is a stop-now condition: unplug the oven and do not use it again.
Sources
General guidance- The Control of Hazardous Energy (Lockout/Tagout) — OSHA 1910.147 and manufacturer service manuals, fetched
Nearest pages
What this page does not cover
One limitation worth stating up front: this page is written for the Black+Decker microwave range rather than for your particular unit. It does not name families, model numbers or control revisions. Where a page exists that does, it is more precise than this one and it is linked under Related pages.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
