Fault Finding

Common Electrical Faults at Home: Diagnosis Guide

Published by AFTA Electrical · May 2026 · Fault Finding

Most homeowners encounter the same handful of electrical problems over the life of their property. Some are simple to resolve yourself. Others require a qualified electrician. This guide walks through the most common faults, what causes them, and when professional help is needed.

My RCD Keeps Tripping — What's Causing It?

An RCD trips when it detects a leakage current to earth — which can indicate a fault in a connected appliance or a problem with the circuit wiring itself. Before calling an electrician:

  1. Reset the RCD and note which circuits it protects
  2. Unplug all appliances on those circuits
  3. Reset the RCD — if it holds, plug appliances back in one at a time until it trips again. The last appliance plugged in before the trip is likely faulty.
  4. If the RCD trips with no appliances plugged in, the fault is in the circuit wiring. Call an electrician.

A Circuit Breaker Keeps Tripping

An MCB trips on overload or short-circuit. If one circuit trips repeatedly:

Flickering or Dimming Lights

No Power in Part of the House

Check your consumer unit — one or more MCBs or RCBOs may have tripped. Reset them. If they won't stay on, there's a fault on that circuit. If all breakers are on but part of the house has no power, the fault may be upstream at the main switch or the incoming supply. Call an electrician — and if the main fuse has blown, contact your DNO (UK Power Networks, Western Power, etc.) as the main fuse can only be replaced by them.

Burning Smell from Sockets or Switches

Do not ignore this. A burning smell from an electrical point indicates arcing, which is a fire risk. Turn off the circuit at the consumer unit, do not use the socket or switch, and arrange for an electrician to investigate as soon as possible.

Intermittent faults are the hardest to diagnose. A fault that only occurs occasionally — perhaps when it's damp, or only under certain load conditions — can take significant time to track down. We use thermal imaging, insulation resistance testing, and loop impedance testing to identify faults that aren't visible or obvious.

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Frequently Asked Questions

An RCD trips when it detects a leakage current to earth, usually from a faulty appliance. Unplug everything on the affected circuits and plug appliances back in one at a time to identify the culprit. If it trips with nothing plugged in, the fault is in the wiring — call an electrician.

Most commonly a loose connection in the lighting circuit, fitting, or switch. Can also be a failing LED driver. If multiple lights flicker simultaneously, it may indicate a voltage supply issue.

Yes — a burning smell indicates arcing or overheating, which is a fire risk. Turn off the circuit at the consumer unit immediately and don't use the socket until it's been inspected by a qualified electrician.

Yes — if an MCB or RCBO trips, you can reset it yourself by switching it back to the on position. If it trips again immediately or repeatedly, there's an underlying fault that needs professional diagnosis.

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