i have a bathroom light and an extractor fan wired into a single switch. i want to be able switch the fan on independatley from the light. the wires in the switch are wired as follows two black one blue into a block three earth into a block three red into bottom of switch and one yellow into top of switch. how do i decide which wires to transfer into the double pole.

dave cleife, February 2010

Disconnect the cable for the fan from the light fitting, and take that to the fan switch.
Replace the 3 core you've just taken out with a 2 core cable, connecting brown and yellow in the same terminal, and the 2 blue wires together, and take that to the switch.

You may be able to do all that in the loft, depending on where the cables go and where you need the switch.

If you want the overun to work don't use a double pole switch.

Adam, February 2010