Light circuit confusion

chillyspoon

chillyspoon

Hey all -

We're having some roofing work done at the moment and one of the roofers needed to disconnect the old exterior porch light, which is mounted in the soffit.

I asked him to safely cap off the wiring to the light, with the plan that I would come back and put in a new light when he had moved on to the next section of soffit a few days later.

You can probably guess where this is going already, he didn't note which of the three wires went where in the old light, and since we have a hotch potch wiring colours in the house (built in the early 1970s) and my limited knowledge, I have no idea what goes where now either - I'd have just snapped a photo when I was disconnecting the original if it had been me doing it!

Here are the details:

• The wiring to the light unit consists of three single core grey sleeved cables going to the light each with a different colour of inner insulation sleeve: one red, one black and one brown.
• The old light unit has live, neutral and earth pole connectors and I don't know if all three were in use or just the L and N.
• The new light is an LED exterior bulkhead light with just L and N connections, no earth connection.

Testing with a Fluke tester I get the following:

With the light switch off:

• Red: Hot
• Black: Off
• Brown: Off

With the light switch on:

• Red: Hot
• Black: Hot
• Brown: Off

This leaves me a bit stumped I've no idea if Brown is actually an earth cable or if it is meant to be doubled up with either Red or Black. Any ideas?

If Brown is the earth, then would I be correct to assign R to the L and Black to the N terminals since red is always hot?

My goal here is to learn as much as solve the problem but I can call in a pro (a friends of ours is a sparks) if this isn't an obvious one or if I'm in doubt about safety/fire etc.

Cheers.