Problem with halogen lighting system - HELP!

[jezb 1]

Novice in electricity here - I have to confess I don't know my volts from my watts from my amps, so bear with me.

Our downstairs WC has 3 low voltage (12V I think) halogen bulbs recessed into the ceiling - the area above this is inaccessible. I do not know how many of the bulbs were working a few days ago but suddenly none of them did. The bulbs are all marked 35W - I replaced one of them with a new bulb of the same spec but still no light, so then I replaced all of them - still darkness. I have an electricity detector and can verify that electricity is reaching all 3 bulb mounts when I turn the switch on - I measured this with a voltage tester and it read 110V all round - but a similar system in the kitchen (with the same bulbs) measures 36-55V all round.

Anyone any ideas ? Could it be the transformer? Problem is this is inaccessible - I'd have to take the whole false ceiling out to replace it.

Given that I'm getting electricity through the wires are there any other types of bulb which might work with the current I am getting?

[verne 1]

the trouble with many voltage detectors and such like is they detect only voltage and do not draw any apprecible amount of current which renders them useless for many tests. clearly if you really had 110 volts coming down the wires the 12 volt bulbs would immediately be rendered useless. when you test the voltage in your kitchen you are testing without a load applied so in an unregulated supply the voltage will often be considerably higher but should be within tolerance if measured accross the bulb while it is operating.

the likelyhood that the transformer is defunct is quite high i should say.

the people who fitted the thing in the first place would not have put the ceiling up around the lights so there must be some sort of access to them from the roof space or floorboards upstairs or through the holes the lights now occupy...

if all other access is denied then you have to remove the lights and carefully draw them down. one of them will drag the transformer into view and allow replacements to be made.

the electrical wholesaler i use says it is best to use one transformer per light these days because experience has taught them cheap multi transformers are rubbish and good ones are stupidly expensive.

if your lights are fitted with fire hoods it is another complication to overcome while fiddling about in those little holes. if there are no fire hoods and the lights are in an enclosed space then you should take advice about whether to fit them...

i hope this helps you.

[jezb 1]

Thanks Verne

It's an odd thing, a few days ago the lights suddenly started working again for no reason, but today they are off again. Could a dodgy transformer cause this phenomenon? Or more likely a dodgy connection somewhere above the false ceiling.

Maybe access was possible from above, but right now the room above is tiled - so perhaps they tiled it after doing the wiring for the room below.

The same switch that operates the lights also operates an extractor fan in the WC, and this is working, so easiest fix for now is to take this off and put a standard light fitting in it's place - at least then we'll have some light.

[verne 1]

i have a friend with the same trouble. her transformer feeds 4 lamps and was working intermittently for quite some time before it packed up completely.

the trouble was the "cheap" 4 way transformer which contained a circuit board more suitable for a cheap radio and not a bit of kit that can get quite warm and in this case carry around 4 amps to each lamp...

are you certain this is a false ceiling? not that it would really make much difference...

if you really can't fiddle one or more of the lamps down out of its hole then one of those live wire detectors might give you a clue where the "hot spot" is. the bit of kit you use to check a wall for live wires before drilling into it.

make a hole in the ceiling near this point to do the work through. the shape of hole is important because a piece of plasterboard bigger than that must go up through it accross its diagonals and then be glued down with some no-nails. another bit of plasterboard is then carefully cut to fit the hole and glued to the previous bit, the gaps are then filled and the whole lot painted to match to complete the repair...

alternatively as it is a loo and not a main room, how about cutting a neat hole and fitting a small access hatch in case you need to do further maintenance up there...

as i tried to explain before; in order to operate a bulb you will need both volts AND amps. although you have a truck load of volts present there will be a miniscule amount of amps or the bulbs you have would be destroyed. or in other words i suggest you do not pursue that line of thought because it will lead nowhere and waste the time you should be spending doing a proper repair...

sorry!