View Full Version : Shock from wall switch. Help!

09-01-2007, 02:38 PM
Hi all. I need some help diagnosing a problem that has recently cropped up in my home. On occasion, I get a very light shock if I happen to touch one of the screws that holds the trim plate to the wall switch. Nothing has been touched with it in several years. There are (2) single pole switches in the box. One goes to outside porch lamps, the other goes to a wall outlet inside that a lamp plugs into. I checked the neutral to ground at the switch and I checked the ground at the wall outlet, my little neon tester indicates the ground is good. I have a multi meter, also if that will help me w/ the diag.. Is this just a defective switch or is there another issue? I don't see any loose connections or damaged wires at the switches but I did not pull them all the way out yet.The wires attach on the sides and are visible. Any knowledgeable help would be appreciated. Thanks............TSport :confused:

Bob NH
09-01-2007, 05:48 PM
Is the shock transient or sustained? If transient it could be that you are generating an electrostatic charge.

You could plug in an extension cord on a different circuit and see if there is voltage between the screw and the ground terminal on another circuit.

09-01-2007, 06:41 PM
The shock is sustained. I think I will try the extension cord. If voltage is present, what next? Thanks.

09-01-2007, 07:23 PM
The screws that hold the cover plate on often are connected to the frame of the switch that, when attached to the box (assuming it is a metal box) would then be grounded. Sounds to me that you might have a hot lead touching the box, and the box isn't grounded properly. If the box was hot AND grounded, it would short out and trip the breaker. This could happen many ways, one of which is not using the proper clamp to bring the wire into a box (i.e., a nick in the insulation). or maybe a loose or too long stripped wire.

Bob NH
09-01-2007, 07:29 PM
The shock is sustained. I think I will try the extension cord. If voltage is present, what next? Thanks.

It appears that there are two problems. Something is putting voltage on the ground wire, and the ground wire is not grounding. You could also have an open neutral with all of the power returning through the neutral.

The problem could be in a device plugged into the circuit. Check any plug-in devices with a grounding plug.

09-01-2007, 08:23 PM
The requirement to ground switches was added to 380-12 in the 1999 code cycle.

If this house was built before that this time there would most likely not be a ground in the switch.

Change all the switches in the box making sure that there is no exposed wires touching anything other than a bare equipment grounding conductor which will connect under the green screw on the switch.

09-02-2007, 08:21 AM
The house was built in '55. I replaced both switches in the box approx. 10 years ago. There is a ground wire present but I did not attach to the switch. I figured the screws that hold switch to the box were adequate since the box is grounded. Maybe I am wrong. I'm going to swap out both switches anyway, hook up the ground to the switch & recheck everything. I was reading somewhere that if there is excess dust present in the box it can act as a conductor. Guess I'll clean everything out real good, too. Anybody want to chime in on the dust theory?
Thanks all for the input. Further suggestions welcome!.........TSPORT :)

09-02-2007, 09:34 AM
Listen to JAD, he has you looking in the right direction!

Neutral current on a ground while very common, generally (espically in a resident) will not achieve enough potential between the grounds give a notocable shock.

Do the extention cord recommendation.

09-02-2007, 06:22 PM
I swapped out the switches (probably fine but I had some new ones laying around and they are dirt cheap), checked all the wires & connections in the box and ran ground wires from each switch to the box and made sure the ground wires from the circuits were intact to the box. Did the extension cord test: no voltage and also verified the ground continuity from the other circuit I plugged the extension cord into to the trim plate screw. All seems fine now. I'll see how it goes. Thanks again!..........TSPORT