Microwave faults explained: not heating, sparking, noisy, not starting

A microwave has very few moving parts, so most faults fall into a short list and each one points fairly clearly at a cause. Here is what the common symptoms usually mean, which you can check safely, and which need a technician. In every case the first step is the same: switch off at the socket and unplug before you touch anything beyond the door and the tray.

Runs but does not heat

The light comes on, the turntable turns, the fan hums, the timer counts down — and the food comes out cold or barely warm. This is the most common microwave fault and it sits on the high-voltage side: the magnetron, the high-voltage capacitor, the diode or the transformer. Weak heating that has got slowly worse over months usually means a tired magnetron. Sudden no-heat after a loud pop or a burning smell usually means the diode or capacitor.

There is nothing here to check yourself. The capacitor can hold a dangerous charge long after the plug is out, which is why this is the one appliance where "just have a look inside" is a bad idea. A Not Heating diagnosis is ₹399 on our rate card; it covers testing the magnetron, capacitor and diode, and the technician tells you which part has gone and its MRP before fitting anything.

Turntable not turning

If the glass tray does not rotate, food heats unevenly — hot at the edges, cold in the middle. Before calling, check three things: the tray is sitting properly on the coupler in the centre, the roller ring underneath is in place and free of food, and nothing has slipped beneath the tray. A stuck grain of rice or a spill that has dried under the ring is a surprisingly common cause.

If the tray is seated and still does not move, the small drive motor or the plastic coupler has failed. A Turntable Fault is ₹350 for the labour; the motor and coupler are low-cost parts.

Sparking or arcing inside

Flashes of light, crackling, a burning smell. Stop the oven at once. The usual causes, in order: metal in the cavity (foil, a spoon, gold trim on a plate, a twist tie); the waveguide cover — the small mica sheet on the side wall — soaked with grease and carbonised; or a chip in the cavity paint where bare metal is exposed. Coastal homes see the paint-chip version more because rust gets under the enamel.

A Sparking Inside visit is ₹350: the arcing point is cleaned and the waveguide cover replaced if it is burnt. Keep running a sparking oven and you risk the magnetron, which turns a small job into a large one.

Noisy operation

A microwave always makes some noise — the cooling fan, the transformer hum, the turntable motor. What changes matters. A grinding or clicking that follows the tray is the roller ring or motor. A rattle is often a loose tray or something under it. A much louder, harsher hum than before, especially with weak heating, is the magnetron or transformer on its way out. A Noisy Operation job is ₹350 and covers the motor, fan and loose-part fixes; if the hum turns out to be the magnetron the technician will tell you before going further.

Not starting at all

Power is on, display is lit, but pressing start does nothing, or it starts and stops. Check the door closes fully and the latch clicks; microwaves have interlock switches and will refuse to run if the door is even slightly open. Check child lock is not on. If the door is fine, the likely causes are a failed door switch, a blown internal fuse, or the control board. A Not Starting diagnosis is ₹350.

Door or latch trouble

Broken latch hooks, a door that has to be slammed, or one that springs open. Do not prop it or tape it; the interlocks exist so the oven cannot run open. This is a parts job for a technician and falls under Not Starting.

Dead display

Nothing at all — no clock, no light. First check the socket with a lamp or phone charger, and the MCB. In Nellore this often follows a power cut: the surge when supply returns blows the internal fuse. If the socket is live and the oven is dead, it is the fuse, the board or the low-voltage transformer. Importantly, a fuse often blows because a door switch has failed, so a good technician finds out why before replacing it.

Quick reference

Symptom	Usually	Rate card
Runs, no heat	Magnetron, capacitor, diode	₹399
Tray not turning	Coupler, motor, seating	₹350
Sparking	Metal, waveguide cover, paint chip	₹350
New loud noise	Motor, fan, loose part	₹350
Won't start / dead	Door switch, fuse, PCB	₹350

Parts are extra at MRP and shown to you before fitting. If two or more of these faults arrive together on an oven past eight or nine years old, read our repair-or-replace guide before spending.