Kitchen LED lights start to flicker when i isolate the extractor fan

1 Aug 2018
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United Kingdom
I am replacing the extractor fan in the kitchen. It has a fused isolator switch. When i switched it off to be able to get to the extractor fan safely, the 8 LED ceiling lights start to flicker.

Switch the isolator back on again and flicker stops!

There is no dimmer on the LED lights, just an on/off switch.

Any ideas on what may be causing this? Is it normal?

Could it be related to the fact that the extractor fan may be connected to the lighting circuit and when the isolator is on, even if the extractor fan is off it still draws some current?

Could it be something more sinister?

Help greatly appreciated!

Thank you

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No its not normal. It could be something very simple (like a loose connection inside the isolator, if the lights are looped in after the isolator then that would be feasable), or it could be something very odd (isolator wrongly wired).
Isolate at CU, unscrew the isolator switchplate, confirm dead with your multimeter and show us the pics
Do you mean they're "on," and they start to flicker "off?"

Or do you mean they're "off" and start to flicker "on?"

Different causes, and different remedies.
Thanks John and OldButNotDead (i like your username)

The isolator just has a single cable and seems it does its job. No reading with the meter when off. I will post picture next

John, LED lights flicker when they are on.

I removed the extractor fan last night
Nothing is connected to the supply. So now LED lights flicker when ON independent of the isolator.

Seems that when there is a load flicker stops....

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Picture of extractor fan.


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What voltage and size are the LEDs? Can you put an incandescent lamp into one of them?

Usually I'd be thinking a loose connection in a ceiling rose or switch, but the fan effect is odd.
I attach picture of the lights... and drivers...

7w lights
Voltage AC 85 - 265V 50-60 Hz

Attached to LED driver....i took a picture and it does not look good. Plastic has melted! The other 7 are ok.

Input. LS 85-265 V 50/60 Hz
5-7 x1 W
Output. DC 12-24 V 300ma
Pictures attached


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7w lights
Voltage AC 85 - 265V 50-60 Hz

Why do manufacturers print such misleading rubbish,

300mA = 0.3 Amp

0.3 A x 85 V = 25.5 watt, ( bit more than 7 watt )
0.3 A x 240 V = 72.0 watts

The 300 mA refers to the current that the lamp drives through the LED elements and NOT the current taken from the mains supply.
It does not make sense, lamp is 85 to 265 volt so one would think connected direct to mains, and the 300 mA driver would normally power 4 to 8 LED,s (not lamps the LED chip) in series they don't seem to go together.

I wonder if the white driver module enclosed inside the lamp housing or attached to the outside as part of the lamp.
Thank you for pointing out the obvious.

Feel like an idiot not realising that led lights should have been connected to mains.

Previous owners set ot up and as soon as we moved in we had lamps flickering. Overheated transformers (no wonder why!) And one blew up!


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