The signs that mean stop and isolate now are a burning smell, scorch marks, a socket that is warm to the touch, and any buzzing or crackling. The signs that mean book an inspection are frequent tripping, flickering tied to appliances, a fuse board with rewireable fuses, and round-pin sockets or fabric-covered flex.
- A warm socket is not normal. Switch off at the board and stop using it.
- Burning smells with no visible source are the most serious item on this list.
- Frequent tripping is the system working, but it is reporting something.
- An old board is a prompt to test rather than proof of danger.
Act now
1. A burning or fishy smell
The most serious sign here. Overheating electrical insulation gives off a distinctive acrid or faintly fishy smell — some plastics used in accessories produce it as they degrade. If you can smell it and cannot find an obvious source such as a scorched appliance, switch off at the consumer unit and call an electrician. Do not wait to see if it goes away.
2. Scorch marks or discolouration
Browning or black marks around a socket, switch or at the consumer unit mean heat has been generated where it should not be. The usual cause is a loose connection: a poor termination creates resistance, resistance creates heat, and heat degrades everything around it. Stop using that point and have it looked at. Scorching at the board itself is more urgent again.
3. A socket or switch that is warm
Accessories should be at room temperature. Warmth means current is doing work it should not be doing, almost always at a loose terminal. A socket that is warm with a high-load appliance plugged in is the classic precursor to the scorching above. Unplug, switch off at the board if you can isolate that circuit, and get it checked.
4. Buzzing, crackling or sizzling
Electricity should be silent. Any audible noise from a socket, switch or the consumer unit indicates arcing — current jumping a gap, which generates serious localised heat. This is a now problem, not a next-week one.
Book an inspection
5. Frequent tripping
A device that trips occasionally is doing its job. One that trips repeatedly is reporting a condition — deteriorating insulation, a failing appliance, water somewhere, or simply too many circuits sharing one RCD. It is not dangerous in itself, because the protection is working, but it is telling you something that needs tracing rather than resetting.
6. Lights flickering or dimming with appliances
Lights dipping when a kettle or shower comes on indicates voltage drop, which can mean a loose connection, an undersized or overloaded circuit, or an issue at the supply. Occasional slight dimming on a big load is not unusual; a persistent or pronounced flicker, especially on one circuit, is worth testing.
7. A fuse board with rewireable fuses
A board with ceramic fuse carriers and fuse wire has no earth leakage protection at all. It is not automatically dangerous — it protects the cable, which is what it was designed to do — but it offers nothing if someone touches a live part or a cable is damaged. It is the clearest prompt for an inspection and usually for an upgrade.
8. Round-pin sockets, or fabric-covered flex
Round-pin sockets predate the modern 13A standard and indicate wiring from the 1950s or earlier still in service. Fabric-covered or rubber-sheathed cable is the same era, and its insulation becomes brittle with age — it can crumble when disturbed, exposing conductors. This is the finding most strongly associated with needing a rewire.
Ranked by what to do
| Sign | Urgency | Action |
|---|---|---|
| Burning or fishy smell | Immediate | Switch off at the board; call today |
| Buzzing, crackling, sizzling | Immediate | Switch off that circuit; call today |
| Scorch marks or discolouration | Immediate | Stop using it; call today |
| Warm socket or switch | Immediate | Unplug, isolate, call |
| Frequent tripping | Soon | Narrow it down, then book testing |
| Flickering tied to appliances | Soon | Book an inspection |
| Rewireable fuse board | Planned | Book an EICR; likely upgrade |
| Round-pin sockets / fabric flex | Planned | Book an EICR; likely rewire |
The top four share a cause: heat where there should be none, nearly always from a loose connection. They are also the four most likely to cause a fire, which is why they are grouped together.
Things that look alarming but usually are not
- A slight click when a light switches on. Mechanical, normal.
- A faint hum from a dimmer or a transformer. Common, particularly with LEDs on an older dimmer. Worth changing the dimmer, not an emergency.
- One LED lamp flickering. Usually the lamp or an incompatible dimmer, not the wiring. Swap the lamp first.
- An RCD tripping once in a storm. Supply disturbances happen. Repeatedly is different.
- A warm plug on a very high-load appliance. Slight warmth at the plug itself can be normal; warmth at the socket is not.
- An old-looking but sound board. Age alone is a prompt to test, not evidence of danger.
What to do between noticing and the visit
- Isolate what you can at the consumer unit rather than at the socket, and label what you have switched off.
- Stop using the affected point entirely — do not just move to the other socket on the same faceplate.
- Photograph any scorching or damage. It helps the electrician and matters if an insurer becomes involved.
- Note the pattern: when it happens, what is running, whether weather or time of day correlates.
- Do not open anything up, and do not attempt a repair on an accessory showing heat damage.
- If there is any smell of burning you cannot account for, switch off at the main switch and call.
What testing will tell you
Most of these signs are symptoms whose cause is not visible from the surface, which is why the answer to several of them is an EICR rather than a repair.
Testing measures insulation resistance circuit by circuit, which reveals degrading cable before it faults; checks earthing and bonding; confirms RCDs disconnect within the required time; and verifies that a fault would actually trip the protection quickly enough. It turns "the lights flicker sometimes" into a specific finding on a specific circuit.
It also distinguishes the two states people conflate: an installation that is old-fashioned, and one that is unsafe. Plenty of older installations are the former. A good report says which you have.
What it costs
These are the electrical figures published across this site:
| Job | Typical Coventry guide price | Notes |
|---|---|---|
| EICR (3-bed) | £150–£300 | Safety certificate |
| Emergency call-out | £80–£100 first hour | Urgent faults |
| Electrician, hourly | £45–£90/hr | Certified, Part P |
| Consumer unit upgrade | £450–£700 | RCD protection |
| Full rewire (3-bed) | £3,000–£6,000 | Whole-house |
Anything in the immediate group above is emergency work and is charged accordingly. The planned items are better dealt with as a scheduled inspection, which costs less and tells you more.
The top four are same-day work. The rest are best dealt with as a proper test rather than a call-out.
Frequently asked questions
Why does my socket smell like fish?
Some plastics used in electrical accessories give off a faintly fishy smell as they overheat and degrade. It is a recognised warning sign of a loose connection generating heat. Stop using that socket, switch the circuit off at the consumer unit, and have it looked at promptly — it is not something to monitor.
Is a warm plug socket dangerous?
A socket that is warm to the touch is not normal and should be treated seriously. It usually means a loose terminal creating resistance and therefore heat, which is the pattern that precedes scorching and, occasionally, fire. Unplug, isolate the circuit if you can, and get it checked rather than continuing to use it.
Do old fuse boxes need replacing?
Not automatically, but they are a strong prompt for an inspection. A rewireable fuse board protects the cable but offers no earth leakage protection, so there is nothing to disconnect quickly if someone contacts a live part. An upgrade is usually the single biggest safety improvement available — after testing the circuits behind it.
Are flickering lights a sign of dangerous wiring?
Sometimes. One LED lamp flickering is usually the lamp or an incompatible dimmer. Lights across a circuit dipping when a large appliance starts indicates voltage drop, which can mean a loose connection or an overloaded circuit, and that is worth testing. Persistent flickering on one circuit is the pattern to act on.
How urgent is a scorch mark around a socket?
Urgent. Scorching means heat has been generated at that point, almost always from a loose connection, and the condition that caused it has not gone away. Stop using the socket, switch off the circuit, and arrange for it to be seen promptly rather than at the next convenient time.
My house is from the 1970s. Does that mean it is unsafe?
No. Age is a reason to test rather than a diagnosis — houses of the same era test very differently depending on what has been done since. What a 1970s installation commonly lacks is RCD protection and earthing to lighting circuits, both of which an EICR will identify and both of which are addressable without necessarily rewiring.
If in doubt, isolate and ask
Four of the eight signs here are same-day work. We will tell you honestly over the phone which category you are in before anyone is dispatched.