Lights gone dim

[Ray H]

We've had energy efficient bulbs in the fittings of both lights in our lounge diner for several years. There are three bulbs in each fitting. They were changed to the newer style bulbs when we ran out of the old style filament bulbs. Consequently, one fitting's bulb's were changed over some while before the other.

 

The replacement 7W bulbs in the first fitting have always been a little on the dim side but the second fitting's 8.5W replacements were/had been much, much brighter. That is until the day before yesterday when the brightness of all three of the 8.5W bulbs suddenly dropped, probably below that of the original 7W bulbs in the other fitting.

 

I could possibly understand one bulb losing brightness as a pre-warning of its upcoming failure but for all three to go at the same time seems strange.

 

Can anyone indicate why this might have happened please? I drew the line at asking for someone to throw some light on this change 😃

[J. S. Bach]

A wiring defect in the supply?

[kevinlms]

Use your multimeter to check the AC power at a power point. That will tell you if the voltage is correct or low.

[Ray H]

Thanks for those two responses.

 

The voltage to the light fitting both direct or via the switch measures 233v.

[Hastings Thumper]

I has a similar scenario a while back with three led spotlight bulbs in the same fitting. One of them started to fail albeit intermittently, and would flash on and off when the power was turned on.  After a couple of days, all three started doing the same.

 

I checked back to the original failing bulb by a process of elimination and once that one was replaced, all was fine again.

 

I suspect its some sort of radiated emissions from the failing bulb which are picked up by the electronics in the other bulbs, or something transmitted very locally over the power lines.

 

So might be worth checking your bulbs one by one in the fitting to see if you can find a suspect.

 

Hope this helps

 

 

 

[tigerburnie]

LED lights lifespan is measured up to the point where they drop output by 30 percent, so it may be yours have reached that point. There was a time when adverts used to tell you how long they will last, that seems to have vanished. I'm sure I bought some that were supposed to last for over 10000 starts.

[Ray H]

I did wonder about checking them individually in the other fitting.

 

On the other hand I suppose I could remove one at a time from their present fitting and see what that reveals.

 

I'll try the latter first and then the former if necessary.

[KeithMacdonald]

Might be irrevant but I've read elsewhere that mains LEDs are very sensitive to low voltage.

I can recall one time we were having brownouts across the whole of our village.

Old filament bulbs (we still have some) kept working, just a bit dimmer.

Some of the LEDs started flickering then shutdown completely.

[The Johnster]

The working life of an led is measured by the number of times it is switched on and off, heating and cooling causing degradation of the materials, and is presumably affected by changes in voltage as well.  An led installed and left on with a constant voltage should last for it's radioactive half-life, exactly the same as if it is left off, several hundred thousand years in some cases.  All you need to do now is to find a power source that can be guaranteed to provide the correct voltage for that sort of period to see if it works...

[kevinlms]

LED lights can be very strange. A friend of mine had some in her computer room and when she turned them on, they were very slow to 'warm up' to full brightness. If she wanted something urgently, she used a torch!

I suggested that she just replaced them, but didn't want to until they died!

 

As for why Ray's have gone funny, perhaps there was low voltage earlier, which killed them. Or one is funny and dragging the others down - who knows just replace them.

[Ray H]

The lights were still usable, just no longer as bright as they were.

 

I found that we still had a couple of unused bulbs so I removed the three dim ones (dropping one of them in the process 😒) and inserted the new one - full brightness. I restored the dim ones - and discovered that the presumed dropped one was no longer dim nor bright, in fact it wasn't anything other than dead) - and they remained dim and the new bulb stayed bright.

 

It does look as though it may have been a power problem that has caused the original bulbs to dim.

 

Thanks for all the suggestions to try.