spotlight wiring

[shadwell69]

I have a wiring nightmare with two 3-way spotlights.
One light is simply wired off a black wire /red wire (earth cut short) and works fine.
The second light in the room has 2 cables coming out of the ceiling, each cable has a black wire red wire and the two earths connected together. Tried connecting two reds into brown lightwire and two blacks into the blue. Fuse blew on upstairs light circuit. What am I doing wrong please?

 

[Chri5]

Sounds like a switch wire issue.

Try wiring just one set of wires on 1 twin and earth to the light. Does the light stay on?

If not try the other set, one or other will be the true LN feed.

Once this has be sussed, you need to terminate the live cable N to the lamp, the L then needs terminating to the L / red of the other cable. This then sends the L down to the switch and the N side of this cable becomes the switched live and is terminated on the L of the lamp.

The switched live should be sleeved in brown sleeving for future ID, a bit of ins tape with a marker pen is sort of ok.