anyone have ideas regarding the best way to locate a possible drywall fastener that has penetrated an nm cable? i would imagine that to be the problem. with the ground wire connected to a light switch people are getting the 'buzz'. thx for any help. ken m

Ken,

What do you mean by "getting the 'buzz'" ?

Bill

bill, just hick talk for getting shocked when touching the cover screws. i did find the problem. a poor wiring job to begin with because the equip gnd was snipped off the supply cable. the gnd wire in the 14/3 feeding the light/fan combo from the switch was terminated on the switch gnd screw and and the fan housing with a potential of 120v. found that the nm cable clamp had been overtightned to a point of mashing not only the nm sheath but the wire insulation of the ungrounded wire as well to a point of contact between the hot wire and the clamp.
not sure why they went to the trouble of grounding the fan and switch and omitting the main equipt gnd cond from the source.

ken,

Gotcha!
It seems like the 14/3 that is made now cannot take tightening of the Rx clamps. The dimple probably digs into it. I always try to give a few wraps of tape around the cable before tightening the clamp.

Bill

At least you have clamps on boxes for Romex.

The equivalent cables here are just run through a knock-out with a rubber grommet so there's nothing to actually clamp the cable firmly. It should be clipped close to the box, but frequently isn't, so strained connections inside are quite common if someone's tugged at the loose cable.