This is basic, but the post is longish. I replaced the light switch in my house because the ceiling light would not come on. It still does not after switch replacement. Old switch tests as good. Using a two-wire device with a small lightbulb, I have tested the switch hooked up in off position, and the test light does not light up. On other switches in the house it does light up. I also tested other ceiling light sockets with the same device and the test light comes on. The light socket in question yields a no-light on the test device. My question: Is there a break or short in the wire from the switch to the socket, or is the socket bad? Related question: How do I find out where the possible break or short in the wire is located? Any help is appreciated, thank you.
Probe the switch box itself with your test light, from hot to neutral. If there is no power there, then the fault is between the box and the distribution panel (fusebox). If there's power to the switch, and power on the output side of the switch when it's "on", but still no power at the socket, then the fault is between the switch box and the socket. In that case, you'll have to open the box the socket is mounted in and check its connections, or go into the attic and check the wires.
You probably have a bad socket. Some switches only have the hot (Black) wire in the switch box. The neutral goes directly to the light socket. So a light test probe will not work across the open switch unless the socket is good and a bulb is in the socket to complete the path. Cut the wires off the light socket, strip them and turn on the switch and test the bare wires for voltage. You should get something if the wires are good. Try not to become part of the circuit.
sockets "wear" out, specially if you use a 100W bulb in a socket rated at 60W. The inner metal "spring" weakens with age and does not make a good contact. replace the socket assembly, here they cost $4.50 or so. rw
Nobody has mentioned this, probably because it is so obvious: did you replace the bulb? Depending on how you use the test light and how your circuit is wired, the test light won't light up if the bulb (or the wiring) is bad. Below, the hot feed goes first to the junction box containing the switch on 2 wires. From that junction box it goes to the junction box where the light is installed on 2 more wires, so there are 4 wires in the switch box, not including any ground wires.
/ AC hot (black wire) --------o o------------+ A B | AC neutral (white wire) ------+------+ | C | | | | +-BulB-+
Using a test light connected at the points I labeled A & B, the light will not glow if the bulb is bad. To say you have no power to the switch may be wrong - it depends on how you used the test light. If you have the wiring shown above, the test should be from A to C to determine whether you have power to the switch.
It can also be wired like this:
AC hot (black wire)--------------+ | +-------------+ A | [Switch] | +-------------+ B | [Bulb] | AC neutral (white wire) ---------+
In this case, the AC feed goes directly to the junction box where the light is installed. The black wire feed is connected to a "switch loop" to go out to a different junction box where the switch is installed, then back to the light fixture junction box. Testing from A to B won't make the test light glow if the bulb is open. And, depending on the test light and the size of the bulb in the circuit, you may not see the test light glow even if the bulb is good.
People have mentioned a bad socket - and that may very well be your problem. Be extra careful before messing with it. You have no indication to tell you when the power is definitely off, because the light isn't working. Kill the breaker for that circuit before touching the wiring. If you don't know which breaker it is, kill them all. Better to kill the breakers than yourself.
Thanks to ALL who responded. Thank you, Ed, for the diagrams. I am going to have an electrician look at it. I do not have the knowledge or equipment. All of the posts have made me more aware of just how dangerous this can be for one who really does not know what he is doing. Again, thanks to all of you!