Dimmer switch problem?

[al]

I've got a dimmer switch that controls a chandelier with three 60W bulbs in it. One blew a few days back and I didn't have a spare. Today, another one blew. Now, the last one has gone ... except it hasn't!

Realised when I took it out that it was 40W where the other ones were 60W. In fact the bulb was fine when I tried it elsewhere, so I nicked two other working ones from another light and it still won't come on at all with three working bulbs.

I then took the dimmer off the wall to test it was still live ... which it is. However nothing happens. Now there's a sticker on it saying that it's rated from 60W-400W min/max load. Have I killed the actual dimmer switch because the single 40W load of the last remaining bulb was too much (little) for it over time? Is that possible? If not, what else can I check?

a

[Dave Plowman (News)]

Dimmers normally fail full on - ie they don't dim. But you can check this by either replacing the dimmer with a switch or just connecting the two wires together. With the power off, obviously.

[Mike Harrison]

Too little wattage will not damage a dimmer, it just may not work properly. Could be that when the last one blew it took the dimmer with it. The most common failure modes of dimmers are always off - internal fuse blown (this may be just a thin track on the circuit board) or always on (triac failed short).

[al]

I did ... with the power on (only a little spark!!). Anyway ... ahem ... it works fine. The dimmer seems to be shagged and doesn't appear to have a replaceable fuse so I bought a new switch. Slightly annoying in that it turns on light notches instead of smoothly, but it was the cheapest I could find at £8.50!

Oh .. and just to rant a little ... why is it that old houses have to have such damned small & shallow housing for switches? There's barely enough room to stuff the cables in, let alone the back of the switch. Grrrr ....

a

[Dave Plowman (News)]

DIY. Fit the box that suits you. I never use plaster depth boxes - or even bother with 1" ones. 1 1/4" minimum.

[Christian McArdle]

Firstly, when candle bulbs blow, they are particularly prone to ionising, giving an extremely large current burst. Often the dimmer takes the full force of this and blows. The circuit MCB may not blow quickly enough to save it. A circuit fuse probably won't blow at all.

It is nothing to do with old houses, but any house that is wet plastered or masonry drylined. The shallow boxes are useful as they are designed to fit entirely within the plaster layer, meaning that light switches don't need to be chased into the masonry, saving time and mess. Socket boxes can't be so shallow, so always have to be chased in.

Christian.