4 red wires in two gang one way light switch

[andyman123]

Hi all, hope you can help. I was simply changing over from a 2 gang one way light switch dimmer to a two gang one way light switch. Cardinal sin, I did not label any cables and did not take a pic #gutted.

I have 4 grey cables coming into the switch back box each containing the old 4 x red 4 x black and 4 x earth. Between the common there is a red small link cable. All of the black wires are terminated into a choc block in the back of the switch.

One switch controls a centre living room light and the other switch controls a wall light - they are not two way lighting.

There are no tapes on any of the cables at all.

If you are able to help that would be much appreciated. I have a multimeter on hand.

 

[EFLImpudence]

The earths should all be connected together and connected to the faceplate if it is metal.
The Blacks left in the connector.

Put each Red in a separate connector block so that they may be tested without them touching anything else.
With the power ON so be careful
Set meter to AC~ to the first setting above 240.

Black probe in meter common terminal - to the Neutral block (the Blacks) and
Red Probe in meter V terminal - to each Red wire in turn and record which ones give a reading of around 240V.

How many Reds are Live?

 

[aptsys]

There's no need to do the tests live, especially for a novice. You can buzz out all of the cables whilst it's dead

 

[stem]

Whilst 'Buzzing out' the cables would be safer, it would be much harder for a novice to do.

 

[andyman123]

Thank you all. I ran some tests, including continuity tests also and all is solved. 4 x red wires 1 to L1 and com (left side) 1 to L1 and com (right side) and link between com left and right side. All is working fine.
I did not live test.
Note to self - pic and label the cable - every time.

Many thanks to you all.

 

[EFLImpudence]

I don't know why there would be a link between the coms.

Remove it and see if it makes a difference.

 

[ban-all-sheds]

I don't know why there would be a link between the coms.

An outbreak of numptyism in the previous household?

 

[aptsys]

Whilst 'Buzzing out' the cables would be safer, it would be much harder for a novice to do.

Clearly not.

 

[securespark]

I don't know why there would be a link between the coms.

To give continuity between the loop in and loop out?

 

[ban-all-sheds]

An obvious reason overlooked by a couple of numpties here?

 

[EFLImpudence]

Yes, of course. To both.

 

[securespark]

 

[EFLImpudence]

Can't think of everything at once.

 

[securespark]

You & me both!