Landing light fitting only registering 120v?

[Jason Arthurs]

I've recently replaced the light fitting in our bathroom, everything worked fine and yesterday evening I noticed the CF bulb at the top of the stairs was sitting a little wonky in its bayonet fitting. I straightened the bulb and as I did it, the light flickered and went out.

I changed the bulb and still no luck. I've now replaced the pendant fitting as the old one was very discoloured but I'm still unable to get the light to work.

Checked both the upstairs and downstairs switches with a meter, the switches all work OK and the voltage at the switches is registering as

220v. At the light fitting however the voltage is 110v with either of the switches in the on position but it registers around 26v in the off position as well.

I have the lighting circuit running on a 5A MCB and this has not tripped. All the upstairs and downstairs lighting works fine including the new bathroom fitting.

Any suggestions on this?

Jason.

[Christian McArdle]

It is likely that you have disturbed the loop through connection (or some other connection) to the stair light fitting when fitting the bathroom lights. The voltages you are measuring are probably just spurious inductive pickup. It is just as likely to be a disconnected neutral as a live.

Christian.

[Set Square]

It sounds to me as if you have somehow managed to wire this light fitting in parallel with one of a pair of other lamps wired in *series*!

[Stefek Zaba]

Going slowly here... the 26V-in-off-position tells me you're using a digital meter with very high input impedance, and you're reading capacitive pickup; which in turn suggests the 110V with the switches 'on' may be a similarly high-impedance (i.e. naff-all current available!) reading.

Have you tried measuring the voltage at the rose, rather than (as I'm guessing you're doing) at the lampholder? Any chance you loosened the live feed to the corridor rose when you were doing Stuff in the bathroom? What voltage do you read across a real (incandescent) bulb connected across the corridor L-N when the switches are 'on'?

[bigcat]

the switches in the on position >but it registers around 26v in the off

use a proper analogue multimeter, end of problem.

NT

[Jason Arthurs]

The readings were taken at the rose with no bulb attached.

Regards, Jason.

[Jason Arthurs]

Doesn't fix the fact that the light fitting no longer works though...

Regards, Jason.

[Christian McArdle]

If you attach the bulb, it is likely to give more accurate readings. Then measure from earth to live and earth to neutral, with the bulb turned on. If both read 240V, then you've lost the neutral. If they both read

[nightjar]

I thought that was a bit of an odd voltage for a landing light, then realised I wasn't on an aviation group.

Colin Bignell

[Christian McArdle]

But in any case, it is irrelevent. You've almost certainly miswired the bathroom light by failing to pass the permanent live and neutral onto the next light in the chain, the failed light in question. Alternatively, the wire was damaged during the process. I assume it is all modern PVC cable, not crappy old rubber?

Christian.

[Christian McArdle]

It's actually quite a normal voltage to find its way to a landing light, if it is run off a nominal 115V AC busbar, as installed on pretty much anything big enough to have turbines.

Christian.

[Dave Plowman (News)]

Wonder if you've dislodged some wiring while fitting your new light? And could there be another not working? Because two non working lights would give a reading of about 110v if they'd ended up in series and you measured between them.

[nightjar]

I'm more used to light aircraft.

Colin Bignell

[bigcat]

it wil enable you to fix it

[Christian McArdle]

It's far more likely to be reactive pickup, though. Particularly due to the

27V reading as well. Also, the bulb doesn't come on at all. 110V on a 240V bulb should be visible.

Christian.