Bathroom Extractor Fan Still Working but Light Doesn't?

Postby fergieboy » Wed Aug 31, 2016 7:55 am

Hi, the extractor fan still works but the halogen light doesnt. I thought i could just change the bulb but no joy.
I believe there is a transformer involved. As you can probably tell i havn't got a clue so any help / advice would be appreciated!
We are putting the house on the market shortly so I am under severe wife pressure to a) sort it myself or b) get someone in to sort it :)
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Postby ericmark » Wed Aug 31, 2016 8:28 pm

Yes there could well be a device for dropping the voltage, if the bulb says it is 230 volt normally these have a bayonet fitting (GU10) then no voltage dropper, if the lamp comes out by removing a ring and it has two pins normally 5.3 mm (G5.3) apart then likely 12 volt and there will be a voltage dropper.

Note:- both are called MR16 out of interest it means it has a multifaceted reflector and is 16 x 1/8 of an inch across. It does not refer to voltage or way of connecting the lamp.

So the voltage dropper can be either of two types. The toroidal transformer is a large heavy unit, often round. The so called Electronic transformer which is not really a transformer is much smaller and lighter and will often fit through the hole that the lamp is fitted into. With the power off, you may be able to renew the Electronic transformer through the lamp hole.

As said not really a transformer but a switched mode power supply, you don't need to know what that is, but they have both a minimum and maximum output, so using a lamp which is too small will cause them to close down. You can't use LED lamps with them, most are running at a high frequency and have a 1 meter limit on cable length so should be near the lamp.

The other possibility is the fan and lamp are not on the same supply, the building regulations require the fan to work independent of lights if you have a non opening window. But if you used just a pneumatic push button to run the fan people tend not to use it, so to get best of both some electricians use a twin pole switch for the lights one pole works lights, the other pole works the fan with a push switch in parallel with the light switch so you can run the fan without using the lights. If this is done, the lights and fan can have a completely independent supply. I think this is unlikely. But it could happen.

The G5.3 MR16 quartz lamp with Electronic Transformer have really passed there sell by date, swapping the G5.3 to a GU10 and using 230 volt and a LED lamp works far better, and a GU10 lamp holder is likely around same price as an Electronic Transformer so if you can access the 230 volt supply then better to swap to LED.

As to if this is DIY or call an electrician only you know how good you are, so that is up to you. Do remember to switch off power at the mains before having a look, even more so if having a feel with your hand. Standard lamp fitting have a permanent line (live) as well as switched line so if you stick your hand in a hole to fell around, and have only switched off at the light switch, you may touch a live wire. So switch off at the box.
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Postby kbrownie » Wed Aug 31, 2016 9:08 pm

You need to check if the lamp (AKA bulb) is a 230v/240v one or 12V one, this is normally printed on the lamp. Is there more than just one lamp?
Still don't loose/broken conductor, faulty lampholder or tripped/blown fuse!
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Postby fergieboy » Thu Sep 08, 2016 8:25 pm

Thanks guys, the transformer has been replaced and everything is working now, cheers
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