I have an old light fitting I am replacing with a new one but I have a bit of an issue that the old fitting has 4 terminals and the new one has 3.
I am aware of my earth, active and netural wires which are join together (with their respective partners) but I have a switch wire also present which I am unaware of the configuration on the new light as there are only 3 terminals (earth, active, netural).
Any suggestions?

Steph, July 2009

There are 4 terminals in a 'looped' lighting circuit.
In simple terms, they are -
- Earth (bare copper wires with a yellow and green sleeve over them). These sometimes connect to a separate terminal somewhere else on the fitting.
- Live (red or brown wires). Usually 3 wires connected together but could be 2 or 4.
- Neutral (black or blue wires). Usually 2 wires connected together but could be 3.
- Switched Live THIS IS THE TRICKY ONE! (black or blue with a bit of red or brown sleeving on it). Only one wire. This comes BACK from the switch (one of the live wires goes TO the switch) If you cannot identify which wire this is GET AN ELECTRICIAN TO LOOK AT IT or you may damage your wiring by getting it wrong.

This all being good the light fitting wires (the ones that go to the bulb(s) which will be blue and brown go to the neutral and SWITCHED live wires respectively.

John (NICEIC electrician), July 2009