Wiring and extractor fan befuddlement

Extractor fan fitted approx a year ago as part of bathroom refit. Electrician added an isolator switch near the light switch. Extractor is in the roof. I remember it worked very briefly then stopped.

I got a replacement from the supplier and just refitted it this morning. Neutral/Switched Live and Live are grey/black/brown, just as it was wired up before (I took a photo).

The fan started up as soon as I switched the isolator on, the room light was still off. Room light made no difference to the fan going on/off but the timer on the fan would disguise that.

Isolator off, fan stops. Isolator on and let it run, it stops after a minute and won’t restart.

So the wiring must have an error if my switched live is permanently live. Great. Might be beyond my experience to try and remedy that.

Would a simple mistake be likely to kill the fan though? Seems to have killed two so far. And I’m unlikely to get another fan from the supplier on warranty.

So time to get a professional in?

One of those screwdrivers with a neon light in will let you check if you have a switched live, constant live and a neutral. Unscrew the isolator switch and check that it’s got both lives in and connected properly.
Standing on a ladder with rubber feet will stop the neon thing working unless you are in contact with an earth though.

Thanks BigJohn. Isolator looks ok – in that all the greys are going to N, blacks are going to L2 ad browns to L1.

I’ll get hold of one of those pens – sounds like one would be useful in the long term. Although the lines in the loft couldn’t be tested in this way unless I hold an earth cable up to me.

I tried swapping LS and L at the fan, didn’t make a difference. Swapped back. Fiddled with the timer and the fan has come back to life – although again permanently on instead of on/off with the light switch. Bah.

Pics here

At the fan (yes it’s isolated, yes I still wear gloves anyway, sometimes)

At the isolator switch

At the light switch

Hard to tell from the photos but shouldn’t the light switch be in series with the switched live to the fan?

I assume that’s a ring main with a switched fused spur for the fan?
Best thing I find to do is get a bit of paper and draw it out so you can see how it should work.

Absolutely not an electrician but it looks like there might be a cock up somewhere in the isolator switch wiring. Looks like light switch is wired L1 through to N, but obviously I can’t see everything from the photos.

If you’re going to do it yourself then check if it’s all wired up like this:

I think you’ve got L1s and L2s back to front and as above not sure about the light switch. Best bet is find wiring instructions for everything and start from scratch.

The light switch has nothing to do with it, the connections will be in the light fitting. It sounds like a loose connection to me.
You really need to find out which is permenant live and which is switched. I am presuming you have it so that the fan only runs when the light is on?
The permanent live is for the run on after you turn the light off.

I had similar last week at work, fan not working, when I undid the switch, and angled it down, all was fine, when back in place, no power. It was a faulty isolator switch. I’d be checking the connections at the light fitting first.

Thanks all. It was wired up by the sparkie who binned all the instructions. I have very little experience with domestic wiring. I can understand circuit diagrams and all sorts but for some reason domestic stuff is counterintuitive!

Being connected to the light fitting makes sense as to why there’s no extra wires at the light switch.

I checked all the connections at the isolator switch and they’re sturdy. Connection issues at the light itself makes sense, I’ll have a look there. Probably something funny going on there, it’s a LED bathroom glove job off amazon.

Thanks again, really appreciate you taking time out of your saturdays to help a numpty.

Further to my post above, I’ve not looked closely enough at the picture of the isolator.
The feed is looped into the switch. The 2x 2 core and earth cables (brown blue and earth) are likely to be the feed in and feed out. The cable to the left, is the cable going to the light. It has a permanent live, brown, switched live, black and neutral, grey.
The one that is mostly out of shot, and connected to the top of the switch is the outgoing feed to the fan. Brown is permanent live, black the switched live, and grey the neutral. They really should be colour marked to avoid confusion.
Anyway, your connections at the fan should be Grey to N, black to LT, brown to L. I am assuming the switched terminal is marked as LT, which I’d guess as being right if I was doing it without instructions.
If the supply is a bit flaky still, then you will need to check both the brown and black connections at the light fitting.

Alan, thanks. That actually makes a lot of sense.

IF there was funny stuff going on at the light, I figure it would have tripped the RCD.

I did test the isolator switch using a light bulb but can’t see what else could be going wrong.

I do have a spare isolator switch so that might have to go in tomorrow.

Cheers again.

I am presuming you have it so that the fan only runs when the light is on?

That is what I had assumed and that is how the other bathroom that the same sparkie did. But the isolator does seem to be wired as if it’s just spur’ing the fan off as an on/off switch? If I can’t see anything funny going on at the light then it must be?

Sorry, it’s so obvious when I look at it, I was just expecting it to be much more complex.

Yes, sort of.
The isolator switch has permanent Live and Neutral to supply the fan. It also has a switched live, which comes from the light fitting, to turn it on/off. The black wire, going to the top middle connector on the isolator, should be connected at the switched live at the light fitting.

Sparky here, you really need to find the light fitting where everything meets, it’ll make sense to you then.

This is why I wire everything at the switch, stupid idea to have everything in some random light fitting, or worse; a hidden junction box with screw connections.

At the light fitting – I’m not sure this helps much. There is a junction box in the loft that might be connected, I shall report back later.

That is a dangerous mess and needs to be dealt with properly. Looks like live wires just twisted together under that tape.

You say an electrician did that? Disgraceful. I’m an amateur and can see several things that are just wrong