The short answer
When a Black+Decker microwave does this, a live display with a dead start proves the supply and moves the whole fault to the door circuit or the control. A lock, a mode and a power cycle are all free; a worn keypad is a part and a door switch is a service call.
What you actually see
- It starts only when the door is pushed hard — A start that depends on door pressure convicts the latch.
- The oven beeps but the cycle never begins — A beep with no cycle means the control heard you and something else refused.
- It trips the breaker when plugged in — A trip on plug-in ends owner diagnosis immediately.
- The clock resets whenever the oven is used — A control losing power under load points at the supply.
Causes, ranked for this microwave
- A mode, lock or timer left set — Leads the ranking — a timer set instead of a cook time does the same thing — the display counts and the oven never runs. Where this checks out clean, treat the next entry as the working theory rather than a possibility.
- Control left in a stuck state — Close behind — a brief interruption can leave a simple controller mid-state, and it is the cheapest thing on this list to rule out. A clean result here does not just remove one part; it removes everything that depends on it.
- Membrane keypad worn through — A step down — the tell is a panel where some buttons work and start does not, which no supply fault produces. It is worth being sure about this one rather than half-sure, since everything after it assumes a verdict.
What to check, in order
- First — the control state — Hold each button for several seconds in turn and watch for a lock symbol appearing or clearing.
- Second — a full power cycle — Note whether the fault returns immediately. An immediate return rules the power cycle out cleanly.
Checks an owner can do safely
- Step 1. Test every button — Press each button in turn and note which respond. A dead start button with a live number pad is a keypad fault.
Tools: noneAbout 5 min
- Step 2. Inspect the cord and plug — Unplug the oven and run the cord through your hand, feeling for flat spots and checking the plug pins for heat discolouration.
Tools: noneAbout 10 min
- Step 3. Check the breaker and protection device — Look at the panel and any protection device on the circuit, and reset once. A device that trips again is reporting a real fault.
Tools: noneAbout 10 min
Before you open anything
Safety
Unplug the oven before anything else. A microwave stores enough energy in its high-voltage capacitor to be dangerous with the cord in your hand. Do not remove the cabinet, do not hold a door switch closed, and do not run the oven with the door damaged or ajar.
When this becomes a service call
Stop and call when the next thing to do meets any of these. Call, or replace the oven, when the outlet is live, the latch is sound, no mode is set and a proper power cycle changes nothing.
Sources
General guidance- The Control of Hazardous Energy (Lockout/Tagout) — OSHA 1910.147 and manufacturer service manuals, fetched
- Article 210 — Branch Circuits — NFPA 70 (National Electrical Code), fetched
Nearest pages
What this page does not cover
Read this as generalized information. It is accurate across the Black+Decker microwave range, which is exactly why it stops short of the detail a single family or model deserves. If a family-level or model-level page exists for your unit, that page supersedes this one on wiring, part numbers and error-code meanings; the links under Related pages are where those pages live.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
