I need a bit of help with a snap action switch. I'm talking about a NOS bakelite switch with S6 lamp indicator and metal diffuser. I've been using one such switch in my living room charging station for about 3 years when all of a sudden it started making arcing noises, the pilot light was flickering and the chargers were probably not happy. I have inspected but not taken anything apart other than the faceplate and lamp. The lamp heats up quite a bit. There seems to be a whitish heat residue (can't think of a better term) on the brown bakelite, and there also seems to be an oily residue on the switch lever (the part that says ON and OFF). There is also some heat discolouration on the switch lever.

I did a bit of research and found references to heat that extracts a plasticizer from wire insulation. The result is an oily substance on electrical components. The neutral wires have a bit of discolouration as well since they are connected very close to the lamp part. All wire in this unit is standard 14 gauge solid copper (Romex). I am thinking of replacing the entire wires in the switch box, as well as the switch (I have some spares). I will use the new one with a LED lamp because of the heat. What do you think ? I really don't want to put a modern switch in there because the indicators don't light up enough.

Now for the NOS switches, could it be that they are bad if they got some humidity through the years (not in my house, but in their previous location before my purchase ? There seems to be a whitish residue on the lamp contacts (the neutral part) in at least one of my spares. Sorry I don't have pictures at the moment.

As for the load, there are three duplex outlets, one of which has built in USB charging ports, and another of which has a standard MacBook charger always plugged in. Would there be kickback in the charger transformer that could damage an old heavy duty snap action switch ? The switch is routinely toggled with a computer plugged in, as well as USB charging devices (iPad or iPod of some flavour).

Thanks for your thoughts.

Bakelite takes quite a lot of heat damage before it starts to give in by itself. However the heat does make it more breakable. If it is only a little discolored near where the lamp was heating it, and nothing is cracked, this could not cause deformation at the switch contacts part - there gotta be an unrelated fault there which caused the arcing. Something like contacts bent out of place over years of bumping into each other or dirt accumulation that prevents one of them from going fully into its intended position. If its been arcing continuously when on it might have been damaged badly from such arcing

The oily substance is bad - Replace all the related wiring, maybe to high temp stuff. I dont think it is good for the bakelite either - id try to clean it off

Unfortunately the unit is sealed shut so I cannot clean the contacts. I will probably end up replacing it along with all the associated wiring. I will use a LED lamp for heat issues, and hope for the best.

Is it really held "sealed" by anything more than a few bent tabs ?

Not sure, will check and report back.

OK, a bit of research : some batches of standard wiring can have the plasticizer ooze out of the insulation under heat. Other batches do not and manufacturers don't seem to know why. When it does ooze out, in can coat the insides of electrical devices (switches, receptacles, banks of circuit breakers, etc). Replacement of the wires and the devices is the only remedy. The plasticizer leaves an oily greenish residue. I wiped mine with clean white paper towel and the residue was greenish. There you go for that one. If I remember correctly, I read about this on the Eaton website.

Now for the old switch, I cannot take it apart. There is a single screw on the back and it goes in the opposite end of the threaded hole for the cover plate screw. When I turn the screw on the back, the threaded hole turns with it and takes it nowhere. So much for that.

I have a few spares, so I took another one and replaced the wires and switch. The new one (identical model) has a different click, as if it snaps with more confidence than the old one. I hadn't really noticed but the old one would turn on with more of a 'pook' sound rather than a nice 'click' like the new one. This leads me to believe it was arcing more than normal. When turning off, the old one had a very slight 'ping' to the sound (a cross between a standard snap action switch and a fluorescent starter) while this one has the same confident 'click' as when turned on. Hopefully this one will last.

The new wiring is from the same batch as the old one (I have a roll of it) but the lamp will be replaced with an LED in account of the heat.

There is a certain amount of some type of grease in these switches, probably to lubricate the mechanism. Now would the orientation of the installation have something to do with my problem ? Mine is installed horizontally whereas the standard installation is vertical. Here is a picture of my installation.

I have multiple Fluorescent luminaires with the leaking plasticizer problem

Strips from 1990 (been in service till ~2011) - http://www.lighting-gallery.net/gallery/displayimage.php?album=2158&pos=111&pid=59041

Troffers from 1993 (been in service till ~2006) - there it was Black-ish. Those were from a different manufacturer and time of installation, but came from the same building as the strips. dont know if its related

Troffers from 2003 (been in service till ~2016) - there it was Black-ish too and lots of it - like the amount from wires plugged into a tube or starter socket was sufficient to completely flood the socket inside and out

One thing i noticed, small insects tend to be attracted to the stuff and sometimes partially dissolved remains of them can be seen stuck to the substance



In a Russian home improvement forum i have read about batches of NM cable (the Russian standard equivalent of) which were, as they called it, "crying". IIRC the story, the cables were making mess in the luminaires, wiring devices and panels about a year after installation in new homes. Users were concerned about the wires losing their dielectric strength and arc tracking in the walls, leading to fire - The manufacturers replied that the "crying" cables dont lose their electrical properties and are safe to leave in service (though i would not trust it...)

I can look for the story and translate it if it is of interest



Can you screw another screw into the insert from the other side to hold it still while undoing the screw ? Or solder a thick wire to the insert if it is made of Copper or Brass, to use as a handle ?

The "non confident" sounds mean that there indeed is a mechanical problem inside. All switches must emit confident clicks

Looking at my example with the FL lanterns, it looks like the plasticizer leakage can happen at the cold areas too (for example - at the starter socket, which is barely above room temperature in normal working - The starter is cold and there is only little heat from the working lamp outside the strip body). Maybe it is accelerated where isolation is freshly stripped or by some electrical effects - this i dont know. I would prefer to not put any of such wire in permanent use, unless i am trying to recreate a haunted house with cursed electrics...

In switches i opened (which are, well, switches, but are of common European designs and probably different from US/Canada switches) there is a little grease around the pivot point of the moving contact, and on the "sliders" from the switch handle that push it into the switch states. There are no means of grease retention anywhere, so the only thing keeping it in place is that it does not run by itself. Apparently it is sufficient this way i.e. universal install position

Regarding the leaching plasticizer, it can be found indeed in cold parts of the wiring. The information I read stated that it could travel from the hot part of the wire (where it is extracted) to colder parts through capillary action between the conductor and the insulation. It can, if enough accumulates in the live parts of switches, cause some arcing. That is why they recommend replacing the switch along with the wires.

AS for screwing something, I tried and it only works to tighten, if I try to loosen it just unscrews the screw. I might try sometime to open it, I saved it.

I have used some of the wire from this batch elsewhere in my home with no apparent problems. I have some that is readily accessible in louvred fluorescents and I might keep an eye on those, especially near magnetic ballasts, to see if the same problem manifests itself there.

Would an inductive kick from a permanently plugged in laptop charger make things worse by sustaining an arc for longer than normal ?

Yes laptop power supplies have huge inrush currents for the first few milliseconds while they form a magnetic field in the core of the transformer and charge there capacitors, the inrush can be up to 70 amps for 3 to 10 mS, while this won't blow a 4 amp slow blow fuse (Type T fuse) it will cause issues with a faulty switch... Even those small switched mode wall-wort type supplies to charge your phone can pull in 25 amps for 3 to 10 mS...   

OK, what about a standard outlet with built in USB ports ?

If they rely on a switched mode topology they will have large inrushes for the first few milliseconds until the thermal PTC heats up, increases it's resistance and drops the current to a safe level, basically if you look at a switched mode, when they come online they are nothing more then a dead short across the transformer so the first part of the cycle gets hit pretty hard, then they come to life switching and reducing current very quickly, they all have built in, inrush protection, but it's only so fast and everything in the power supply is built around this inrush so it's not a huge problem and the grid will survive, if your switch is having an issue with them you could use it to switch a relay (contact), or even better a solid state relay with zero cross detection (they turn on at the start of the AC cycle not the top of the cycle, so you have 0 volts and 0 current) but they also allow for leakage across the triacs/scrs inside so they will present voltage at the plugs but very little current, and some items may not like this..   

All the USB built in plugs I've used seem to fail, and the ones from Costco those 2.1 Amp two packs are the worst and failed in under a week, but they do have a great return policy, I took one back out of the two pack and they refunded me for both, so now I have a free surge protected outlet with a dead usb charger... 

There is no inductive kick there as they are switching power supplies, not big transformers. The inrush current kick is as explained by Lodge from the capacitors charging up

In USB chargers the power is often so low that they skip on PTCs and use just a 10-ish Ohm resistor (which also acts as the fuse for the module) or no resistor at all and rely on the capacitor ESR. Receptacles with built in ports are meant to be always energized, so maybe they have even less inrush limiting than pluggable chargers. But it really depends more on the product design and quality and not on whether it is built in or not

@ Ash, If the switched mode supply didn't use a diode bridge to convert AC to DC before switching they would behave like a transformer when turned off but the diode bridge stops that, this is also why they don't care if you feed them 50/60 Hz or even 400 Hz input power..

@ Sol just throwing this out there, have you considered changing out the snap switch to a mercury switch, they don't seem to have contact issues very often and have the same retro styling, and they are so quite and smooth you'll think it's broken for the first year...   

I think I'll replace that USB outlet, just to be sure.

As for mercury switches, I won't consider it as the main reason I have that configuration is for the star pattern the pilot light makes with an S6 lamp in a metal guard.

It is not the diode bridge that stops the kick. Its mainly the "way out" for current through the diode on the secondary, the suppressor (RDC network) on the primary, and if anything still comes out, it is sinked by the big filtering cap on the primary

The diode bridge would not stand up to any inductive kick anyway, it would just break down - and possibly followed with catastrophic failure, in case the input power from the low impedance utility supply happened to be applied again at the very same moment (for example during the moment when the plug is inserted into the receptacle and connection can make or break several times over a few 10's or 100's mSec)

Would a Mercury switch even exist in a "to be mounted sideways with receptacle faceplate" format ? After all it have to be installed in a specific position, or else it wont work