A while back, I replaced an old switch in the bathroom. Everything was fine up until yesterday...the wife was showering and the circuit tripped. I inspected and even bought a new switch. When I connect the wires and it is NOT screwed into the box, it is fine. As soon as it gets screwed into the box, it hums, sparks and trips the circuit.

The box itself is loose, so I am assuming the issue is behind the box in the wall. I have everything either taped or I applied some liquid tape to ensure nothing is exposed.

Any thoughts on what else it could be before I tear apart the wall to replace the box?

Thanks!

 

If it is Romex, loosen the screw that secures the cable, to the box & try to pull the cable. Hopefully, you'll see where it's cut.

 

Welcome to the forums.

How about some pictures? http://www.doityourself.com/forum/el...-pictures.html

 

My first guess would be that a cable has been pinched, worn or cut through where it comes into the box clamp and the slight movement of screwing in the device causes the cable to short out. Is the switch right up against the shower? Some kind of plumbing leak or significant humidity and condensation in the wall could be making it worse.

 

Thanks for the replies. Even if the box is motionless, just touching the screw to the box shorts it. In the back I just put some liquid tape since the wires are old and may have cracked. It is not near the shower, but my assumption is that the humidity played a part. The strange thing is, it works fine, as long as it is not screwed into the box.

 

Is the switch damaged or arced up internally? If you set your multimeter to the continuity/resistance setting and measure between the metal mounting strap on the switch and each of the screw terminals do you get a reading?

 

Na, I went and bought a new switch and hooked it up...same result. And these are heavy duty switches, not the $1.xx ones...I spent like $7 on it heh

But yeah it is that old metal clad cable. If it was not in the bathroom with tile, I would have tore it all apart and just ran new romex. I did that for another switch with old wire. I just ran new romex, problem solved.

 

It looks like the wire is shorted where it leaves the metal jacket. Can't quite tell if the red thing I labeled is actually a bushing. It also looks like the clamp has either been cut or burned off.

I would remove the clamp screw and see if there is any slack on the cable. I can see possibly having to remove that box to cut/repair the bx.

 

Thanks for the help all! Ended up taking off the clamp, pulling down more wire, putting in a new bushing, taping it to be sure, and reinstalled the clamp. So far so good.

This old house wiring is frustrating to work with to put it mildly.

 

I have to laugh when people consider houses built in the 60s, old. For most of my life, I lived in places that were built in the 20s or before.

 

I went back to look several times and never saw where the OP mentioned the age of the house. I just assumed this was old BX from the '40s. But, I have to agree. A house built in the '60s is almost new!

 

I always consider the difference between old and new to be balloon framed vs. platform framed, which for houses in my area usually falls right about 1955 - 1960 as the dividing line. Once you hit platform framing that's also when you'll start to see plywood, sheetrock, roof trusses, 3 tab shingles, NM cable and similar "modern" standardized building materials.