The DIY category of posts was meant for me to post about the random odd-jobs around the house that might need to be done from time to time. As it turns out, there often aren’t that many jobs – sometimes the jobs don’t merit covering at all, and other times, they’re the kind of jobs you infinitely defer upon because it’s just a chore.
This job sort-of-fits into the above category. In our house, we have a living room area light which is controlled by a two-way switch arrangement. One of the two switches had gone bad over time, resulting in a very unhappy flickery LED lamp with associated buzzing of arcing contacts. To remedy this, you had to walk to the other switch and toggle it (sometimes a few times) before things would settle down and work once-more. As it wasn’t a critical failure in the sense that it can be fixed by a little extra walking and flicking of switches, it was probably not good for the LED lamp and a bit of an inconvenience.
Spurned on by the fact that my brother had his own beliefs about what caused the flickering, I decided to replace the mechanism itself and solve the problem for good.
Precautions
As this procedure involves working with mains wiring, there is an element of risk involved. You should always de-energize any circuits you are working on by opening the breaker responsible for the circuit (at the least) and verifying that there is no power on the circuit. In the case of my issue, I de-energized the lighting circuit breaker, and flipped the switch a few times to check none of the lights (including the one I’m working on) were receiving power.
Working on mains wiring can also be a problem in regards to the law. In many places, you may have to be a licensed electrician to work on wiring, and it may have impacts upon insurances. This is often disregarded, as mains wiring isn’t quite rocket science, but do so at your own peril.
I will not be held responsible for anything that happens to you as a result of following, or attempting to follow the instructions in this posting. The information is provided in good faith, and you make your own independent decisions. If you are not confident with mains wiring, leave it to a professional.
Equipment Required
To do the replacement itself, you should have the following:
- A small (~4mm) flat bladed screwdriver, preferably fully insulated.
- A PH1 and PH2 Philips head screwdriver, also preferably fully insulated.
- A set of pliers, and a wire stripper or suitable knife in case the wire needs to be re-stripped or shaped.
- A replacement switch mechanism (e.g. this one), or if you’re replacing a whole GPO, the whole GPO wallplate.
It’s important to note that depending on the existing wallplate and switch arrangements, there could be incompatibilities in fit between switches and wallplates of different series. Most of the more generic-looking switches have a “cube” style form factor which is mostly interchangeable, but it pays to check first if you’re unsure.
Also, if you can’t get the switch mechanism alone, it can be possible to buy a wallplate with a number of switches that can be “popped out” to be used as replacements. This can sometimes be more economical. Where the fit is a problem, replacing the whole wallplate might be a good idea.
However, it should be noted that most GPOs have integrated switches which are part of the whole mould, so it’s not possible to borrow a switch from most modern GPOs and use it with a lighting wallplate. This is especially the case as Australia has instituted the requirement that GPOs switch both poles.
The Procedure
Because actually taking photos while working on the wall is a distraction, and de-energizing the circuit for the lights for the house for a significant time would be an inconvenience, these photos are a simulation sans-wires.
Step 1: De-energize the circuit and verify that power has been cut. For your own safety, you should always do this.
Step 2: If your wallplate looks similar to the above, and no screws are visible, then you will need to remove the fascia. To do this, look around the edges for a slot to pry, or otherwise, just find a good place to poke your flat-head in around the edge and give it a gentle helping push. The trim should pop off. If you have an older wall-plate with no fascia but the screws are not visible, they could be hidden behind screw-caps/plugs which need to be removed. A tiny screwdriver may help. If the screws are already visible, then you can move on.
Step 3: You need to use a large Philips driver to remove the two screws securing the wallplate to the wall. Try not to push down on the screws while doing so, as you can deform plasterboard clips or dislodge them. The screws need to be fully extracted.
Step 4: Remove the wallplate from the wall. In some cases, the wallplate may have been fixed for so long and painted over that it just doesn’t come right off. A gentle pry around the edge with the flat-head screwdriver will persuade the unit to come off. A small amount of paint damage is normal. Gently ease the wallplate from the wall without putting too much stress on the wiring behind.
Step 5: Identify your bad switch and remove it from the plate. This can be done with the flat-head screwdriver, inserting it into one of the small slots and gently easing it out. Do not apply too much angular pressure as a crack in this surround will lead to the switch “falling into the wall” in the future.
Step 6: Examine the bad switch and prepare your replacement switch. First, on the new switch, back-out the screws needed to make the connections. In the case of a one-way light, you will need the connections labelled C and 1. In the case of a two-way light, then you will also need connection 2. If the neutral is looped at the plate, then the terminal marked L or loop needs to be backed out as well.
For example, there are the backs of two switches I had on hand. Note the top terminal in both photos is the C terminal, where C stands for common. Most of the time, the active side is connected to C. The terminal to its right from the rear of the switch is labelled 1, and is the first position contact. This is used for one-way light controls, and wiring in this order means that the light turns on when the “10A/250V” text on the front is not visible (switch flipped down). The covered contact to the left is labelled 2, and is the second position contact. This is energized when the first position isn’t – basically it’s an SPDT switch, so when output 1 is off, output 2 is on and vice-versa. This plastic cover can be pried off with a screwdriver for two-way light applications. The final terminal at the bottom is normally labelled L or Loop and is basically an isolated brass terminal used to “hold” and bind together multiple wires (often neutral side connection). This may or may not be used depending on whether your installation is loop-at-the-switch or loop-at-the-light.
On the bad switch, start with one wire. Undo the screw for the terminal of that wire, noting its position. Remove the wire from the terminal. If the wire end is still well formed (in a U bend ideally) and the strands have not broken or been overstressed at the base, then you can proceed to transfer this to the corresponding position on the new switch and tighten the screw until the wire is firmly held.
In the case that a wire does break during removal, you will need to strip an appropriate length of insulation off the end, form the end into a small U loop and then continue as normal. Repeat the process until all wires are transferred to the new switch at the corresponding positions.
Step 7: Align and clip the new switch into the wallplate, noting to ensure the orientation is correct and it is firmly inserted into position until it clicks. Flip the switch several times from the front to make sure it is not going to “fall in”. Remove, keep or dispose of the bad switch.
Step 8: Realign the wallplate with its plasterboard clip holes or mounting bracket and screw into place only as tightly as needed to hold its position firmly. Overtightening can lead to cracking of the wallplate.
Step 9: Refit the fascia. Energize the circuit and test the switch. If it operates correctly, then that completes the job.
Post-Mortem
Having pulled out the defective unit, I thought I’d open it up to take a look inside. The switch cube itself is unbranded, and likely to be a Chinese import unit no more than 10 years old in residential service.
The mechanism is very simple, consisting of the rocker cap pivoting against holes in the outside of the casing. A contact plate straddles a raised central bar common and touches either one of the 1-2 contacts with a lubricated spring applying the necessary pressure to flip the brassy-looking contact plate against either contact.
At some point, it’s quite likely that the contacts had begun to oxidise rather badly, and this resulted in some arcing/pitting of the plate and contacts, making the contact even more “noisy” and eventually failure prone. In theory, you might be able to revive such a switch by cleaning the contacts to a very flat and even finish, and cleaning the contact plate in much the same way, but I suspect it could be something intrinsic to the material used that makes it prone to such failure. The current it was switching was small, even considering in-rush, so such a failure seems rather unusual. Maybe there was a dimensional issue in construction or a weak spring resulting in poor contact “wiping” action.
Conclusion
Replacing a wallplate switch mechanism is not a difficult task, although it is a job that I’ve often deferred. The same procedure can be used to replace wallplate dimmer mechanisms. Replacing a GPO is not much different either. However, you need to remember to take basic safety precautions and work with care especially around other wires. Solid core wires don’t like to be disturbed too much, or otherwise, they fracture leading to “more work” in re-preparing the wires.
When it comes to these mechanisms, there are a lot of cheap Chinese import brand (or unbranded) units such as the ones shown above. The main reason I used them for demonstration was because I had them on hand – however, these do have a fairly known reputation in the industry to be cheap and failure-prone. This is one reason I haven’t put them in my walls (yet, or at all). Based on conversations with a number of electricians, the consensus is really to stick with known good brands, such as HPM or Clipsal, which will last the distance and save future call-outs. I think that’s sage advice given what I just pulled out of the wall …
A lot of switches and relays actually have a MINIMUM current that they are rated to switch (good luck finding that spec for consumer devices). Currents below this may not properly “clean” the switch/relay contacts and they prematurely fail. I wonder if low current LED bulbs are low enough to cause problems? All (300+) bulbs in my house are now LED, but most are on circuits with several bulbs. I haven’t noticed any problems…
That’s true too, especially for relays. But I don’t think it’s going to be much of an issue, as this started in the CFL days and the inrush current of the lamps is still sufficient to my knowledge (i.e. several amps due to primary side capacitor charging. But it could be less for units with no such primary side capacitor, but still, normally the issues only manifest themselves in the sub-100mA range.
– Gough