Replacement light bar fitting - advice required

[honty]

Hi there,

As part of my 'Credit Crunch' kitchen overhaul, I've decided to replace the ceiling lights there.

I have 2 sets of 2 spotlight bars currently, which I'm trying to replace with new spotlight bars. The current ones are connected to a loop in wiring system (the second running off the first)

There are a couple of areas where I need some guidance, however.

1. When removing the first set of lights, the connector strip was squeezed tightly up into the ceiling in such a tight space that I had to unscrew the wires before I could remove it. As a result, I couldn't tag the wires, and Sod's Law, when I eventually managed to get the 3 twin-and-earth cables out, the installers hadn't marked the switch cable! Having read the posts elsewhere on the site, I have tried using a digital multimeter to identify the black switch wire while flicking the light switch, but the reading I get from all the cables tends to fluctuate quite a bit without even touching the switch, before settling down to near zero. Annoyingly, the multimeter doesn't have a continuity test function either.

Am I best off getting another multimeter (with continuity buzzer), or is there another (cheaper!) way I can identify the switch cable?

2. Having looked at the wiring diagrams on the site so far, they all seem to apply to ceiling roses. However, my new lights contain a connector strip with only 3 pairs of terminals which is fixed inside the fitting (see picture below), though the fitting instructions are pretty useless I'm pretty sure that I need to use another connector of some sort.

Can someone tell me how I should wire this up to the three twin-and-earths and whether I need to get any other bits, e.g. a choc box

Many thanks in advance!


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[sparkyspike]

Are you sure you have no continuity setting? Do you have a photo of your meter? If you're trying to test live, which it sounds like you are, then you should stop if you're having problems.

If you don't have a tester with continuity, then get a new one - they're only a tenner.

You have the right idea: with the power off, connect the reds, and look for low resistance to one of the blacks with the switch closed. Then confirm by opening the switch. A chocbox is a good idea if you want to terminate a lot of cables in the ceiling.

 

[ericmark]

You can easy replace the three way connector strip with a 4 way. Any did store sells chock block.

Yes you can test using the light it's self I did make an instruction set on how to do it. But when I started posting it people seemed to get them selves in complete knots. Other electricians could follow it and confirmed not mistakes but only 1 in 10 DIY people seemed to be able to work it out so I would stick with a meter or similar.

Saw one guy using an battery operated door bell.

 

[honty]

Thanks for the replies so far. Yes, I'm pretty sure that there's continuity test setting. I've check the (scant) instructions and tried everything under the sun, but there is no such setting. It's a 'mini' multimeter, so it's probably not a very good one! For testing, when you say 'connect the reds', could you elaborate?

No worries about testing live - all turned off at the consumer unit.

The connector strip is glued into the light bar, unfortunately. I'm a bit of a novice, so could you talk me through exactly how I connect it up, either using a choc box and/or another connector strip, so that all the wires are in the right place and the lights actually work!

Sorry to be such a dunce! Once I know what I'm doing, I'm all right, though.

 

[sparkyspike]

Ok, first to test.

Ignore the new light for now. Connect all red cores in the ceiling together in a terminal block. Attach the red probe of your new continuuity tester to that terminal. With the switch 'on', connect the other probe to each black wire in turn. One should give a low reading (less than 1 ohm). Mark this as your switched live. The others should give a very high reading or open circuit reading.

Now connect this switched live cable into its own terminal. Connect all the other blacks in a third terminal and the earths in a fourth. Wire a new piece of 3 core cable into the four terminals. The live core goes to your switched live. The neutral goes to the third terminal and the earth to the fourth. Nothing goes into the first terminal with the reds in. Do the same connections with the cable coming from the second light.

Put the whole lot into a choc box, leaving the three core cable hanging out of the ceiling for the new light.

This may all be a bit tight for a choc box, so consider using a wagobox instead.

 

[conny]

As a complement to the low reading that sparkyspike says you should get, when you get it switch off the switch and you should get an open circuit reading. This will confirm you have the swiched live.

 

[honty]

That's great, thank you. Turns out that I wasn't connecting up the reds before testing for the switch cables (duh), but on following sparkyspike advice, I located the one black wire that flitted between an open circuit reading and low resistance reading when toggling the switch.

Just need to get myself a chocbox (or similar) and a length of more cable and I'm away!

Thanks again all.