Fault-find a dead socket outlet

Helpful video reference. eFIXX — a UK electrical training channel with more than 280,000 subscribers, producing content for electricians and electrical apprentices — filmed this real fault-finding job in "Electrical Testing and Fault Finding — Socket NOT Working for a Dishwasher". Presenter Marcus and his colleague work through a dead socket from consumer unit check through to dead and live testing, which is exactly the sequence this guide describes. Watching them work through a real job is a good way to understand how the process feels in practice.

1. Check the consumer unit first

Walk to the consumer unit and look at the MCBs (miniature circuit breakers) and the RCD or RCDs. An MCB that has tripped sits in a middle position, neither fully on nor fully off. An RCD that has tripped sits at the off position, often with the button popped out. Reset an MCB by switching it fully off, then back on. Reset an RCD the same way.

If the MCB or RCD trips again as soon as you restore it, there is a fault on the circuit: something plugged in that is faulty, damaged cable insulation, or a wiring problem. Unplug everything on that circuit and try resetting again. If it holds with everything unplugged, reconnect appliances one at a time to find the culprit.

If nothing has tripped at the consumer unit, the fault is somewhere in the circuit itself.

2. Use a plug-in socket tester

A basic socket tester costs a few pounds from any hardware or DIY store and plugs straight into the 13A socket face. A three-LED indicator pattern tells you whether supply is reaching the socket, whether the live and neutral are connected to the correct terminals (polarity), and whether the earth is present.

No indicator lights at all means no supply is reaching the socket. If the tester shows a "live earth reverse" or "live neutral reverse" pattern at a socket that previously worked, there may be a damaged conductor somewhere on the circuit or a loose connection causing intermittent contact.

3. Test the sockets either side of the dead one

Carry the socket tester and check the outlets on either side of the dead socket, working along the wall. If one socket in the middle of a run is dead but the others work, the fault is likely a loose terminal inside that specific socket, or a damaged conductor between it and the next socket on the ring. If a whole run of sockets is dead, the supply has been interrupted further back.

On a ring circuit the supply enters and leaves each socket. A break at one socket can kill everything beyond it on one leg of the ring. You may find that half the room works and half does not.

4. Isolate the circuit and remove the faceplate

Switch off the MCB for the affected circuit at the consumer unit. Use your voltage tester to confirm dead at the socket face — test between live and neutral, and between live and earth. Both should read zero. If either reads voltage, the socket is still energised from somewhere else and you should not open it until you have found that source.

Unscrew the two faceplate screws and ease the socket forward gently. Most sockets have about 50 mm of cable slack behind them. Look at each terminal: are all three conductors (brown/red live, blue/black neutral, green-yellow earth) present and properly inserted? A conductor that has pulled out of its terminal because it was not stripped far enough, or was not tightened properly when last installed, is one of the most common causes of a dead socket.

Also look for signs of overheating: dark brown or black discolouration of the terminal block, melted insulation, or a faint burning smell. These are a sign of a loose connection that has been arcing, not just a harmless fault.

5. Check for a fused spur feeding the socket

Some socket outlets, particularly in kitchens and utility rooms, are not wired directly to the ring final circuit. They are fed from a fused connection unit (FCU) — a switched plate with a cartridge fuse inside, usually mounted higher up the wall or under the kitchen units. The FCU takes its supply from the ring and delivers it to the socket through a spur cable.

If the socket has only one set of cables behind it (one brown, one blue, one green-yellow rather than two sets running in and out), it is almost certainly on a spur. Trace back to find the FCU feeding it and check whether the 13A fuse cartridge inside has blown. Pull the fuse carrier out, remove the fuse, and check it for continuity with a multimeter. A blown fuse cartridge is a few pence to replace — but if the fuse has blown for no obvious reason, something on the spur drew too much current and needs investigating.

6. Check for a junction box in the circuit

Where cables were extended or sockets were added at a later date, the circuit may pass through a junction box in the floor, ceiling void or behind a socket. A loose connection in a junction box can kill everything downstream of it. These are harder to find because the junction box is typically out of sight. If you have worked through steps 1 to 5 and the fault is still unresolved, this is the stage where you may want to call an electrician rather than start lifting floors.

When to call us

A dead socket is often a simple reset or a loose screw. But if the circuit keeps tripping, there is heat damage, or you cannot trace the fault, it needs a proper investigation with test instruments. Richard covers Sandwich and east Kent for fault-finding jobs at the £10 per 10-minute rate for small local work.