Why Do My Bulbs Keep Fusing?

The free checks: swap a bulb and note the pattern

These cost nothing, they are safe, and they turn a vague complaint into something an electrician can act on in one visit.

• 1. Switch off at the switch and let the bulb cool before you touch it. A failed LED or halogen can be genuinely hot. If the switch is a two-way one operated from two places, make sure both are off.
• 2. Do the swap test. Put the suspect bulb into a fitting that has never given trouble, and put a known good bulb into the suspect fitting. Then wait. If the good bulb also fails in that fitting, the fitting or its wiring is the problem, and the bulb was innocent. If the suspect bulb works happily elsewhere, it was never faulty at all.
• 3. Map it. Write down which fittings have failed and how often. One fitting, one room, one circuit, or scattered across the flat — each points somewhere different, and this is the single most useful thing you can hand an electrician.
• 4. Note when they fail. At the moment of switching on? In the evening when the whole colony’s load is highest? After a power cut, when the supply comes back? Right after the generator changes over? Each of those is a clue about the supply rather than the bulb.
• 5. Read the markings. Check the bulb’s cap type and rating against what the fitting is marked for. Check whether the fitting is described as enclosed or sealed. And check whether the bulb says it is dimmable, if there is a dimmer or an old regulator-type switch in the circuit.
• 6. Look at the holder from the floor. Browning or blackening around the holder, a scorch mark on the shade, a bulb cap that comes out discoloured or with pitted metal, or a bulb that has to be wiggled to light. Look and note; do not investigate further.
• 7. Keep one failed bulb. A bulb with a blackened cap tells a different story from one whose plastic body has yellowed and warped, and an electrician can read that.

Then take the pattern you found to whichever section below matches it.

When it is always the same fitting: heat and a poor connection

If bulbs die in one place and nowhere else, the two likely causes are both local, and neither is the bulb’s fault.

• Trapped heat. This is the commonest single-fitting cause, and it surprises people because LEDs are sold as cool-running. An LED bulb contains a small electronic driver, and heat is what kills that driver. The bulb is designed to shed its heat into the air around it. Put the same bulb inside a sealed glass fitting, a tight decorative shade, a recessed downlight box, or a housing buried in a POP false ceiling with no air movement, and it cooks itself. In a Delhi summer, with the room already at 40°C and the false ceiling void hotter still, this happens far faster than it would in a cooler climate. The tell is a bulb whose plastic body has yellowed, browned or distorted, and a life measured in months rather than years. The fix is a bulb rated for enclosed fittings, a lower-wattage one, or a fitting that lets air move — a choice worth putting to the electrician.
• A loose or poor connection at the holder. Where the holder’s contact does not grip the bulb properly, or the terminal behind it has worked loose, current arcs across a tiny gap. That produces heat right at the cap of the bulb and a rapidly fluctuating supply to the driver, and either alone will finish a bulb early. The tells are a bulb that flickers or has to be wiggled, a cap that comes out blackened or pitted, browning around the holder, and a holder that has gone brittle. Do not attempt to tighten or replace a holder yourself — it is live, and it is a small job for an electrician.
• A worn or wrong switch, or a dimmer. An old switch with worn contacts delivers a rough, arcing supply each time it is operated. A dimmer designed for filament bulbs, or an old fan-type regulator pressed into service on a light, will destroy non-dimmable LEDs quickly and often make them buzz or flicker first. If there is a dimmer in the circuit, either fit bulbs marked dimmable and compatible, or have the dimmer changed.
• Vibration. A fitting on a wall that a heavy door slams against, or a light fixed to a ceiling directly under a stair or a water tank, shortens bulb life. This is a real but much rarer cause.

If the same fitting is also warm, discoloured or smells hot, stop using it, switch that circuit off at the board and treat it as urgent — the same logic as a sparking switch or socket.

When bulbs fuse all over the house: the supply

If bulbs are failing in several rooms, on different circuits, the fittings are not all faulty at once. Something is reaching all of them, and in Delhi that usually means the quality of the supply.

• Voltage swings. Delhi’s supply sags in the evening peak and can rise at night when load drops away, and the swing is worse at the far end of a long feeder, in older colonies, and on upper floors of buildings with a long rising main. An LED driver is built to work across a range, but repeated excursions outside that range wear it out early. The pattern to look for is bulbs failing in the evening, lights that visibly dim when a heavy appliance starts, and neighbours with the same complaint.
• Surges when power returns. The moment supply is restored after a cut is electrically violent, and a colony with several cuts a day gives its lighting circuits a great many of those moments. The same applies at generator changeover in a society. If your bulbs fail at the instant the power comes back rather than while running, this is your answer.
• A loose neutral. This is the one to take seriously. If the neutral connection serving your flat or your building is loose or corroded, the voltage on different circuits can swing in opposite directions, and lights can be pushed well above their normal voltage. The signature is lights that brighten and dim in an unrelated way, several bulbs failing across the flat over a short period, and appliances failing too rather than only bulbs. This needs an electrician promptly, and if it is upstream of your meter it needs your distribution company.
• Cheap bulbs with cheap drivers. Worth saying plainly and without naming anyone: the electronics inside a very cheap bulb are what get cut back, and a driver with less protection is the first thing to fail under exactly the conditions above. Buying from a reputable retailer, keeping the bill, and checking there is a real warranty is more useful than any brand loyalty — and a genuine warranty means failures are replaceable rather than just annoying.

Our voltage fluctuation and stabiliser tips explain what genuinely needs protection and what does not, because the answer is not a stabiliser on every light. If the trouble comes with frequent tripping, read why an MCB keeps tripping, and if your flat is old, the signs house wiring needs replacing covers the wider picture.

Why does my LED bulb glow or blink when the switch is off?

A dim glow, or a slow blink every few seconds, from an LED after the switch has been turned off is common and it has a straightforward explanation. It is not a ghost, the bulb is not broken, and it is not usually a fire risk — but it is telling you something about the wiring that is worth acting on.

An LED needs only a tiny amount of energy to produce a visible glow, far less than a filament bulb ever did. So a very small residual current that a filament bulb would simply have ignored is enough to light an LED faintly, or to trickle-charge the capacitor inside its driver until it flashes and discharges — which is exactly the slow blink people describe.

Where that residual current comes from:

• The switch is in the neutral instead of the live. The most important cause, and unfortunately a common one in older Indian wiring. A light switch is meant to break the live conductor, so that when it is off, the fitting is dead. If it was wired into the neutral instead, switching off stops the light working but leaves the holder and the bulb still connected to the live supply. Some current can still find a path, and the LED glows. This matters far beyond the glow: it means that anyone changing that bulb with the switch off is touching a fitting that is still live. It should be corrected.
• An illuminated or electronic switch. Switches with a small indicator lamp, and touch, remote or smart switches, pass a tiny current through the circuit even when off, to power themselves. With a filament bulb nothing showed; with an LED it glows. This one is benign and usually fixed with a compatible switch or a device the electrician fits.
• Two-way and long parallel runs. Where a light is switched from two places, or where the lighting cable runs alongside other live cables for a long distance, a small voltage can be induced in the off wire. Again, invisible with a filament bulb, visible with an LED.
• A leakage path. Damp in a switchboard or a deteriorating cable can also produce it, and this one is not benign. If the glow appeared during the monsoon, or if the RCCB has been tripping, treat it as a fault and read why an RCCB keeps tripping.

Constant trickle current also shortens the bulb’s life, which is why this section sits on this page at all — a bulb that is never fully off is a bulb that fails sooner.

When to call an electrician, and what to tell them

Call promptly if any of these apply, because they are faults rather than inconveniences: a holder, plate or shade that is warm, browned or smells hot; a bulb whose cap comes out blackened or pitted; a bulb that glows or blinks when switched off; bulbs failing across several rooms in a short period; lights that brighten and dim on their own; other appliances failing as well as bulbs; or the MCB or RCCB tripping alongside.

Call when convenient if a single fitting keeps eating bulbs, if a fitting flickers or needs the bulb wiggled, if bulbs in a false ceiling or a sealed fitting keep dying, or if you have a dimmer that hums or flickers with LEDs.

What to tell them so they arrive ready. This job is diagnosed on pattern, so the notes you made are worth more than anything else:

• Which fittings have failed, in which rooms, and how many bulbs each has gone through.
• Whether the swap test moved the fault with the fitting or with the bulb.
• When they fail: at switch-on, in the evening, when power returns after a cut, at generator changeover.
• The bulb type, wattage and cap, whether the fitting is enclosed or recessed, and whether it is in a false ceiling.
• Whether there is a dimmer, an illuminated switch, a touch or smart switch, or two-way switching.
• Whether any bulb glows or blinks when switched off, and in which fitting.
• Whether anything is warm or discoloured — with a photograph, and keep a failed bulb to show them.

What a proper visit looks like. For a single fitting, the electrician isolates the circuit, checks the holder and its terminals, replaces a holder that is heat damaged rather than retightening it, and advises on a bulb suited to an enclosed or recessed position. For a whole-flat pattern, they check the incoming voltage and the neutral connection at the board, look at the lighting circuits, and tell you whether the problem is inside the flat or upstream — and if it is upstream of your meter, that is a matter to raise with your distribution company rather than an electrician.

For how electrical labour is generally quoted across the region, see electrician charges in Delhi NCR. If the fix turns out to involve old switchboards, switchboard and socket replacement covers that work, and where the whole installation is at the end of its life, full house rewiring explains the scale of it. Our electrical upgrades worth doing and home electrical safety tips cover what prevents a repeat.