Light Switch - Overcurrent - Doesn't Switch Off

[andrewc]

Yesterday I was rewiring a part of the lighting circuit. At some point I re-enabled the power at the consumer unit to the lighting circuit, then flicked the switch that controls power to the bit of the circuit I changed. At this point the MCB and RCD both tripped. (I accidentally introduced a short-circuit).

Afterwards, the switch was stuck in the on position, and wouldn't snap back into the off position. Externally (on both the face and the inside) the switch plate looked fine - as in, I didn't notice any visible damage.

This morning I tried again, and was able to flick the switch back and forth between the on and off positions with no problem.

I'm minded to replace the switch anyway, as it seems the safer option, but can anyone guess what might have happened internally in the switch that prevented it from moving between the on and off positions?

I should add that it's a standard 2 gang 2 way (10A I believe?) light switch.

 

[EFLImpudence]

Just welded the contacts together - very slightly - now it's come apart.

 

[slippyr4]

At some point I re-enabled the power at the consumer unit to the lighting circuit

"at some point"

Probably the switch contacts were spot welded together. For the cost of a new switch, I'd replace it as a matter of course - it may become a problem in the future if the contacts are oxidised.

I presume you've found your fault, and rectified it. What, exactly had you done wrong?

 

[andrewc]

Welding - that makes sense.

There's a cable that runs from the light switch to a junction box inside a false ceiling. From there it runs to a million other junction boxes, each supplying a spotlight.

I snipped that cable short and prepared one end of it to connect to another one of the junction boxes, in effect changing where the electricity feeds in from. With the other end I did nothing, so it remained connected to the circuit. When I turned the power on, the live and earth conductors (and possibly neutral as well) must have been shorted together on that other cable at the point where it had been cut.

Once I removed that other shortened cable from the circuit, everything worked fine. Well, except for the damaged light switch.