How to wire new floodlight so it works with the light switch?

From your description, it sounds as though the cable is a 3-core and earth cable, where brown, black and grey are all live conductors (not neutral by default). The colours alone don't identify their function—they should be identified with sleeving and confirmed by testing.

If the floodlight is permanently on, it's likely you've connected the permanent live to the light instead of the switched live. The grey or black conductor may be the switched live, depending on how the original PIR light was wired.

Before making any changes, the conductors should be identified using a voltage tester or continuity testing with the power isolated. Never rely on the wire colours alone, as they may have been repurposed.

If the floodlight no longer has a PIR sensor and is intended to operate solely from the wall switch, you'll typically need:

Permanent neutral to the floodlight's blue terminal.
Switched live from the wall switch to the floodlight's brown terminal.
Earth connected to the earth terminal.

If there isn't actually a neutral present at the light fitting, the existing wiring arrangement may need to be altered. If you're unsure, it's safest to have a qualified electrician identify the conductors and reconnect the fitting correctly rather than guessing, as incorrect connections can damage the fitting or create a safety risk.

Based on the cable colours, it sounds like the old PIR light had a permanent live, switched live and neutral. Without testing, it isn't possible to confirm which conductor performs which function.

I would recommend identifying the conductors with a suitable tester before making connections. If connected incorrectly, the light may remain permanently on or fail to operate correctly from the switch.

What you’ve got is almost certainly 3?core+earth that was used to feed the PIR (permanent live, switched live, and neutral), and by putting the lamp’s blue onto the black you’ve likely connected it to a live (so it stays on); you need to identify which core is (neutral) and which is the (switched live) rather than guessing by colour, because on older/3?core cables the (black/grey may be neutrals or lives depending on how it was sleeved/terminated at the other end), and colours don’t tell you function—safe method is isolate the circuit, open the indoor switch and/or the old PIR wiring point, and test: neutral will be the conductor that’s continuous back to the circuit neutral, permanent live will be live regardless of switch position, and switched live is only live when the switch is on; then wire the new flood as (CPC (earth) to earth, Neutral to blue, Switched live to brown), and any permanent live present should be safely terminated in an insulated connector and not connected to the light—if you don’t have a tester or aren’t confident proving dead and identifying conductors, get an electrician because misidentifying these can trip the circuit, damage the fitting, or leave exposed live parts.

Hi it sounds like you have a 3 core and earth cable running from your switch to the flood light in most cases the brown will be a permanent feed that is why as you switch at the moment it’s permanently on the black cable or the grey will either be a switch line or the neutral cable a simple test will tell you which is which and once you have determined this you can connect up as it should be hope this helps

Open the switch and disconnect the permanent live brown, now at the flood light the black wire need to have brown marker tape and connect this to the brown of the light fitting, brown is disconnect in the switch so dead, blue to blue earth to earth and you now have a working flood light from your switch

Wire earth to earth
Wire blue to grey (neutral)
Wire floodlight brown to black (switch live)

The brown from the supply is a permanent live

Earth to Earth: Both stay connected as before.The Grey (Neutral) to Blue: Neutral from the house to the neutral on the floodlight.The Black (Switched Live) to Brown: Switched live from the house (going through the light switch) to the live on the floodlight.

There will be a switch wire, you will have linked the main live to a permanent live that isnt switched. Please contact a local electrician as doing this without the correct testing equipment may result in electric shock.

First of all the feed that goes to the pir needs to be on the switch and that connects the terminal feed. From there you run a switch line cable from switch to lights. E. G let say 2 core twin to the common that is brown. Earth, neutral in connector block or wagos. That goes for the switch line colours blue and earth. Brown will be L2 Switch line..

The issue lies in how the existing wiring is connected to your new floodlight. Based on the colors you’ve described, it seems that the existing cable is using a 3-core-and-earth wire, likely designed for previous functionality with the PIR floodlight. To make the new floodlight work with the switch, you need to correctly identify and connect the switched live wire.

Step-by-Step Guide

Tools Needed:

Voltage tester

Screwdriver

Wire connectors (if needed)

Steps:

1. Turn Off Power at the Breaker: Ensure the circuit you're working on is powered down at the breaker box to avoid any risk of electric shock.

2. Identify the Wires:

Existing Cable:

Brown: Likely the permanent live wire.

Black: Likely the switched live wire.

Grey: Often used as neutral (confirm with a tester).

Earth: Protective earth (yellow/green).

Floodlight Cable:

Brown: Live.

Blue: Neutral.

Earth: Protective earth.

3. Test the Wires: Use a voltage tester to confirm the roles of each wire:

When the switch is on, the switched live (probably black) should show voltage.

The permanent live (brown) will always show voltage.

4. Connect the Wires: Match the wires as follows:

Earth to Earth: Connect the yellow/green from the house to the yellow/green on the floodlight.

Switched Live (Black) to Brown: Connect the black wire from the house to the brown wire on the floodlight. This ensures the light is controlled by the switch.

Neutral (Grey) to Blue: Connect the grey wire from the house to the blue wire on the floodlight.

5. Cap Off Unused Wires:

If the permanent live (Brown) is not used, cap it off securely with a wire connector or terminal block to prevent accidental contact.

6. Test the Circuit:

Turn the power back on and test the light switch to ensure it controls the floodlight as intended.

7. Secure Connections:

Once everything is working, securely fasten all wires and mount the floodlight.

Common Issues:

Floodlight Permanently On: This usually happens when the permanent live is connected to the floodlight’s live terminal instead of the switched live.

No Power to Floodlight: Double-check the connections and ensure the correct wires are used.

If you’re unsure or uncomfortable, consult a qualified electrician for safety and compliance with local electrical codes.

With the existing cable being 1.5mm 3core and with what has already been mentioned, for the light to work with the switching the brown conductor from the light must be connected to the black of the 3 core making sure brown sleeving is used, the blue conductor from the light needs connecting to the gray conductor of the 3 core using blue sleeving for correct identification, then within the switch once power is isolated disconnect the brown conductor from the 3 core cable out of the switch so that no live conductor are exposed

The black cable maybe you switch wire and the brown will be a constant live

Grey would connect to blue
Brown would be permanent live
Black switch live

The issue is occurring because the brown cable is being used as a constant feed. Under safe isolation, remove the switch faceplate and locate the cable going to the light. This can be done by creating a short at the light and testing continuity between conductors. Once the cable is identified reconfigure the switch so that the brown conductor is on l1 and the grey conductor is connected to the circuits incoming neutral (using a wago). The grey conductor requires blue sleeving to identify it as a neutral conductor.

The remaining black conductor can be placed in a wago. It can be helpful to label it as an unused core.

Then at the light ensure that the grey goes to neutral and brown to live and wago the black. Ensure all sleeving to identify conductors is present.

This is a very basic electrical knowledge question and as such this does highlight lack of competency in dealing with the task. We have to advise that only individuals who are competent in understanding the risks associated with electric shock and fire carry out electrical work per the regulations. We therefore suggest that you hire a suitably qualified electrical and do not advise that you carry out this work yourself.

You need to find out which of the black or grey cores is your switch line the that you would wire to brown and the other to the blue