Bathroom Pull Switch

[stevie2525]

Hi
I have just had to replace my bathroom pull switch after the last one broke. The switch controls 3 spotlights and an extractor fan. Before the switch broke it would turn on the fan and lights at the same time and then turn them both off when pulled again. Since replacing the switch the lights work fine everytime, however the extractor fan only turns on every other time I turn the lights on now. The switch is a 1 way MK switch from screwfix. Only 3 wires blue, brown and yellow/green. New switch is wired the same as old, ie. Brown to COM, blue to L1 and green/yellow to Earth.
Anyone help on what is happening would be much appreciated.

 

[Chri5]

If only 3 wires are at the switch then somewhere above ceiling the live, neutral and earth for both the fan and lights MUST be jointed.

The switch on really interrupts the live, so the 3 wires at the switch represent live / switched live and earth.

You need to access the ceiling and check the joint. Alternatively, and hopefully, remove the light fitting and or the fan covers and look for a joint there.

If lady luck is on your side, your find the joint at the fitting.

If you have loft access you need to get up there and see if anything is obvious (such as the Mrs having just got the xmas tree down and pulled on some cabling etc).

Report back, good luck.

 

[bloxy]

Just an idea.

Could the old switch have been a momentary one to activate a relay? If the new one is a normal latching switch that would account for the every other time behaviour.

 

[ban-all-sheds]

It could have been, but then the lights would also be exhibiting the every-other-time behaviour.

 

[bernardgreen]

The idea of the previous switch being a momentary switch is possible.

I wonder if the lights have an intelligent transformer / controller that toggles between ON and OFF in response to a control input.

With the previous momentary switch a short pulse on the control input ( switched live from pull switch ) toggled the lights between ON and OFF. But if the pulse is too long ( as from a normal switch being ON ) then the toggle function is cancelled and the lights follow the control input.

These exist for lights operated by air bellows switches.

The fan control has a similar toggle function for use with a momentary switch but does not discriminate between long and short pulse lengths so it toggles the fan ON or OFF every time the switch has gone ON-OFF

More details of fan and lights and any boxes connected to the lights are needed to solve this one.

 

[TicklyT]

Just OOI, and maybe nothing to do with the problem....

....Just trying to get my head round the possible consequences of using a fan with a timer, with switched and permanent lives strapped together in the fan... What resets the timer circuit when the light is switched off....

....If the timer circuit requires the switched live to drop to the same potential as the neutral to reset, which it would do very quickly with a GLS incandescent lamp installed, but the OP's lighting is ELV powered by an SMPS, or low energy lighting....

 

[stevie2525]

Hi All

Thanks for replies so far. I'll get up in the loft in the morning and take a look at the connections up there, but to be honest nobody has been in the loft so nothing should have changed. All that happened was the pull switch turned off and then wouldn't turn on again. I've just looked at the old switch and its an RPP 1 way pull switch, has an earth a com and a 1W connection. I have replaced it with an MK 6A 1 way pullcord switch and wired it the same. I'll get back to you tomorrow regarding whats in the loft, I do know there is a transformer up there as they are ceiling spotlights!!!!!

 

[stevie2525]

OK, had a busy weekend so didn't get a chance to go up in the loft, but also everything appears to be working now. I don't know if I'm going mad and its definitely a possibility but from around saturday morning the extractor fan now comes on everytime the pull switch is activated. I haven't changed anything..............its just working everytime now........bizarre.
I'm not sure if its bad, as in something here isn't right, or its good the fact that its now working.

Anyway just wanted to thank you all for your comments though and I appreciate all the stuff that was said.

Steve