Strange things happening with my r/c dimmer switch

[sifu]

Hi all, I've just fitted one of these:
http://www.tlc-direct.co.uk/Technical/DataSheets/Systems/TouchRemote.htm
bought from B&Q, and wired it up as shown in the '1 way lighting circuits' section. The new switch I have has metal casing and is earthed to the back-plate, the neutral wires are also squeezed into the back-plate behind the switch. The switch works fine when it is hanging off the wall, but as soon as I screw it to the back-plate and start to apply a bit of tension to the screws it won't remember the lighting level. When I adjust the lighting level, and then switch the light off and then on again, it resorts back to the lowest lighting level. If I tighten the screws all the way in, the light then starts to randomly switch on and off constantly going bright, dim, bright, dim, or sometimes it steps up and down in brightness as if I have put it in to 'learn' mode even when I haven't touched it. As I said, it works as it should when hanging off the wall, or sometimes even when screwed in to the back-plate very lightly.

There's little room behind the switch and I had to take the old back-plate out and chase some of the wall away so the switch would fit flush to the wall. The wires are squashed in behind the switch and I've tried moving them to various positions but with no luck. I have neutral, live, load and earth. The live, load and earth are connected to the terminals on the switch. As much as possible I've made sure there is no tension on the wires or the switch when screwed back.

Any ideas?

Thanks.

 

[Careful_Bodger]

sifu ..... if this were not a mains circuit with lethal voltages, I would carefully try to flex the switch front plate (while 'hanging free'), and see if the exhibits the same effect. If it did it might suggest a loose connection or broken circuit board inside the guts of the housing. This would not be easily repairable.

Since this is a mains circuit ...etc, this would not be a sensible thing to do due to the danger of electric shock.

The only other thing I can think of is some kind of interference effect - but I cant see why this would be so location sensitive.

HTH

 

[breezer]

i bet the cables are being crushed, or a screw is going through something it shouldnt

 

[sifu]

Thanks for your replies.

c_b I already tried what you suggested but no matter how much I wiggle the cables, or twist the front pate and switch housing, everything works ok. All the basic checks such as polarity, resistance to earth, short circuit and earth continuity check out ok.

Breezer, the cables look ok but it was a bit of an effort to screw the front plate in without any pressure being applied to the wires, there's not much room in there. Visually, the cables seem ok.

I don't know much about electronics so I have little idea how these things actually work, but my first thoughts were that the housing of the switch was pushing against the metal back plate and somehow there is inteference, or the wires were being crushed as suggested. After moving the wires around a bit I can screw the front on nearly all the way and it now works ok, but a further half screw turn and it fails to remember it's luminence setting. I'm going to try to chase a little more wall out and make some more room in there. Will let you know if it works.

TVM for your suggestions.

Have a good Sunday!

 

[ban-all-sheds]

Bite the bullet - remove the existing box, make the hole deeper and fit one at least 35mm deep.

 

[kendor]

certain types of touch dimmer will work by picking up the faint signal that your body has picked up from surrounding electrical equipment and passed through your fingertip to the sensor plate where it gates a device connected to this plate(if you have access to an ocilloscope touch the tip of the probe and you will see this signal).
If this type of touch dimmer then it could be susceptible to pickup from the switchbox when you screw the plate back, as suggested a deeper box may help by making sure the wires are further back away from the sensor plate.

 

[mapj1]

Agreed you need a deeper backox - chisel, 35 or 45mm box and polyfilla. But, could you be earthing the touch plate with the screws as it goes together. Or fit a deep surface box over the top, as a quick test..
M.

 

[muffking]

SIFU: The Varilight is supposed to fit in a standard 16mm box, but only if the wires are really short which is what I had to do with mine (and that was a double). If you want more wires behind the switch then you can easily get away with a 25mm box, but it does sound like the wires are being pulled or trapped.

 

[sifu]

Thanks everyone for your suggestions. I fitted a deeper back plate and made loads of room, but still faulty. I then had another go at checking the switch box and found that pressure applied at a certain angle made it go haywire, I didn't notice this previously. So I've now taken it back and swapped for a replacement and all is ok. It kind of throws you off a bit when a new part is faulty!

Once again, thanks so much for all your help. Have a good weekend!

 

[Careful_Bodger]

it might suggest a loose connection or broken circuit board inside

Smug smug smugiddy smug