The answer, before the detail
On a Black+Decker BMG microwave, no heat with everything else working is one of the few faults where the honest answer is that there is little to check at home. Run the two-minute water test to confirm it, rule out a power-level setting and a door that is not quite closing, and then book it. The cabinet is never opened by an owner, on any model. The BMG key covers more than one build, and for this fault the difference shows in whether your unit has a touch panel rather than a dial.
What you observe on these models
- Everything runs, nothing heats — Confirm with a cup of water rather than with a plate of food.
- Food needs twice as long as before — Weak heating rather than none, which usually means the same components on their way out.
- The sound of the machine has changed — Do not open anything to chase it.
- Settings that were changed and not changed back — The cheapest possible explanation and worth ten seconds before anything else.
- It has to be pushed to latch — An interlock partially engaged can leave the oven running without heating.
- NEAR MISS — nothing happens at all when you press start — If the turntable is not turning, this page is not yours.
Causes, ranked for the BMG build
- The magnetron or another high-voltage component — It leads because on an oven that otherwise runs perfectly there is very little else it can be, and because the symptom is so specific. The fan, the light and the turntable all run from a different supply, which is why they carry on working.
- The door is not closing fully, or an interlock is partly engaged — Second in the practical order, because a door that needs a push can leave the oven running without the part that heats being enabled. A door that must be pushed to latch is the tell.
- Grease-blocked filters or a vent tripping a thermal cut-out — It is ranked here because it explains intermittent heat rather than none at all. The filters slide out and wash in hot soapy water.
- The control board or the relay that enables the heat — Last, because it is less common than the magnetron side and equally out of reach. Indistinguishable from the first cause without instruments.
The order that finds it fastest
- Run the cup-of-water test — Use a microwave-safe mug and never run the oven empty.
- Check the power level and any defrost setting — A low level or a defrost programme heats so gently it reads as nothing at all.
- Close the door and feel for a positive latch — If it does, that is its own fault and its own page.
- On an over-the-range machine, check the grease filters — They wash in hot soapy water and go back damp-dry.
Power off first
Safety
The cabinet stays closed — on every model, for every fault. A microwave oven holds a high-voltage capacitor that can carry a lethal charge after the plug is out, so the only safe work is on the outside: the door surfaces, the turntable, the filters where they are fitted and the outlet it plugs into. Unplug it before touching any of that. Never defeat or tape an interlock, and never use an oven whose door is bent, cracked or no longer closing square.
Where the owner job ends
Call as soon as the power level, the door and the filters are ruled out — that is the whole owner-side list on this fault. The cabinet is never opened by an owner because the capacitor inside can hold a lethal charge after the plug is out, so there is no further step to take at home. Unplug the oven in the meantime and do not run it empty to test it again.
Other faults covered for the BMG models
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
