Baffling light fixture problem

Hi guys,

I'm having a baffling electrical problem—can you help?

I recently upgraded our home's light switches from toggles to rockers. A few days later our front porch light flickered a bit when I turned it on. The switch connections looked fine, so I figured the (CFL) bulb might be getting ready to burn out.

The next day, the light didn't work. A new bulb didn't help. I thought it might be the new switch, but when I removed the light fixture and tested the leads, they had power.

I reconnected the fixture, making sure the wires were securely in their twist-on connectors. No light. I tested the new bulb in another fixture.

So it must be the fixture itself, I thought. But when I connected it to an outlet, it worked.

What could I possibly be overlooking?

I should mention that our house has aluminum wiring. I've been careful to apply anti-oxidant paste to all connections, and everything's worked fine till now—including this fixture, which I installed several years ago. Thanks for your suggestions!

1st) Using an inexpensive VOM from a hdw. store, with the fixture connected and the switch on, the bulb removed and the scale on the VOM set on the A/C in the range above 120, touch the red lead to the center tine of the socket and the black lead to the threads of the socket.
2) If you do not read about 120V, you have a deteriorating and intermittent fixture.
3) If you do read about 120V turn the switch off and with a needle-nose plier reach into the lamp socket and gently raise the center tine slightly and insert the bulb.

Or just go right to step three, without the VOM.

Thanks, but as I mentioned, the fixture does work when I plug it directly into an outlet (via an extension with no female end).

So, don't follow the suggestions, by a new fixture and when that one doesn't work either
maybe you'll have learned something.

CLUE; The correct use of a VOM to accomplish voltage tests.

Short tempers today? Hmmm?

This is not like re-wiring the Space Shuttle . . .

If the fixture works, you must not be getting power from the switch. If you don't have a tester ("magic wand") for presence of current, you can get one at Gome Depot for around $10. It will tell you if you have current from the swicth to the fixture when it is turned ON. If you get no reading, you need to fix the switch connection or the switch itself.

I use my tester constantly on remodeling work. It should be in your tool kit if you are messing with switches and outlets.

Good luck.

zepper said:

Hi guys,

I'm having a baffling electrical problem—can you help?

I recently upgraded our home's light switches from toggles to rockers. A few days later our front porch light flickered a bit when I turned it on. The switch connections looked fine, so I figured the (CFL) bulb might be getting ready to burn out.

The next day, the light didn't work. A new bulb didn't help. I thought it might be the new switch, but when I removed the light fixture and tested the leads, they had power.

I reconnected the fixture, making sure the wires were securely in their twist-on connectors. No light. I tested the new bulb in another fixture.

So it must be the fixture itself, I thought. But when I connected it to an outlet, it worked.

What could I possibly be overlooking?

I should mention that our house has aluminum wiring. I've been careful to apply anti-oxidant paste to all connections, and everything's worked fine till now—including this fixture, which I installed several years ago. Thanks for your suggestions!

Click to expand...

When you tested for voltage, did you check between hot and neutral or between hot and ground?

zepper said:

So it must be the fixture itself, I thought. But when I connected it to an outlet, it worked...

Click to expand...

Snoonyb said:

1st) Using an inexpensive VOM from a hdw. store, with the fixture connected and the switch on, the bulb removed and the scale on the VOM set on the A/C in the range above 120, touch the red lead to the center tine of the socket and the black lead to the threads of the socket.
2) If you do not read about 120V, you have a deteriorating and intermittent fixture.
3) If you do read about 120V turn the switch off and with a needle-nose plier reach into the lamp socket and gently raise the center tine slightly and insert the bulb.

Or just go right to step three, without the VOM.

Click to expand...

zepper said:

Thanks, but as I mentioned, the fixture does work when I plug it directly into an outlet...

Click to expand...

Snoonyb said:

So, don't follow the suggestions, by a new fixture and when that one doesn't work either... maybe you'll have learned something...

Click to expand...

Dude, the fixture is fine. I've tested it indoors several times now and the light always goes on immediately and stays on steady. It sounded like you were just telling me to buy a meter to do the same thing.

What's more, in both of the testing outcomes you described, you cited faults with the fixture. Then you concluded by (facetiously) saying I could skip the meter-testing, just buy a new fixture, and that it wouldn't work either—implying the fixture was not the problem. So it seems like you even contradicted yourself.

It's too bad that ridicule can't improve my ability to read your mind or your ability to write more clearly... Otherwise I might be able to understand you by now.

zepper said:

[from my first post] I thought it might be the new switch, but when I removed the light fixture and tested the leads, they had power.

Click to expand...

CallMeVilla said:

If the fixture works, you must not be getting power from the switch. If you don't have a tester ("magic wand") for presence of current, you can get one at [Home] Depot...

Click to expand...

I may seem like a noob, but yes, I am indeed using a tester—not, for example, my fingers, or the cat. :?)

AlwaysOneMoreProject said:

When you tested for voltage, did you check between hot and neutral or between hot and ground?

Click to expand...

The fixture has just two leads (no ground), so there's no ground lead in the box. I have tested the positive power lead and the box's ground screw, though, and I get power there as well.

I've just been back out there tonight. I've tried another new switch (even though there's power at the box). I've re-re-re-tested the fixture on another outlet, and it works fine. Nothing's changed...

I've just called a friend who does electrical work and he can't figure it out either. I just thought you guru-types might have a clue. If you don't, please don't feel obligated to put me down, as my wife is already handling that task nicely.

Which box has the live wire comming to it, just a guess but if the power comes to the light first, have you checked for power at the switch. AL. is brittle you may have broke a wire in one of the boxes. If power comes to the switch first, I have no clue.

nealtw said:

Which box has the live wire comming to it, just a guess but if the power comes to the light first, have you checked for power at the switch. AL. is brittle you may have broke a wire in one of the boxes. If power comes to the switch first, I have no clue.

Click to expand...

How can you tell which place the power comes to first? Wouldn't you have to be able to see through the wall? And if I'd broken a wire, there wouldn't be power at the fixture box, would there?

Sorry to be such an amateur about all this—there's probably some simple explanation I'm just missing.

If the power goes to the light first there will be two sets of wires, 2 blacks nuted together one white to the light and the other white to the light. So power comes in on one wire goes to the switch and back to the light so you have black and white to the switch. If power is going to the switch first, you have two blacks to the switch and the whites are nuted together and the light has a black and a white connected to it. Keep in mind, Im just grabbing at straws too.

The point of my previous responses to you was to urge you to obtain V.O.M.
If you have not elected to take that advice, you will continue along the failed efforts you are now engaged in.
Because a continuity test is one of procedures you engage in to eliminate the cause of failures.
OBTAIN A VOM!

nealtw said:

If the power goes to the light first there will be two sets of wires, 2 blacks nuted together one white to the light and the other white to the light. So power comes in on one wire goes to the switch and back to the light so you have black and white to the switch. If power is going to the switch first, you have two blacks to the switch and the whites are nuted together and the light has a black and a white connected to it. Keep in mind, Im just grabbing at straws too.

Click to expand...

It should be black and white nutted together and a black and white going to the fixture for a switch loop.

Yes; Joe is right about the loop
The other questions are , are there any red wires anywhere in this system? and if you have power at the light box, does it go away when the switch is turned off. And how meny switches are in the switch box?

nealtw > If the power goes to the light first there will be two sets of wires, 2 blacks nuted together one white to the light and the other white to the light. So power comes in on one wire goes to the switch and back to the light so you have black and white to the switch. If power is going to the switch first, you have two blacks to the switch and the whites are nuted together and the light has a black and a white connected to it...

6 wires come into the switch box: one white and one black for each of the three switches. None of them are nutted or connected to anything else.

At the light box, there's one white and one black lead. There are also two other black wires in the back that are nutted; I didn't use them because the fixture I replaced wasn't using them.

Snoonyb > The point of my previous responses to you was to urge you to obtain V.O.M. ... If you have not elected to take that advice, you will continue along the failed efforts you are now engaged in... Because a continuity test is one of procedures you engage in to eliminate the cause of failures... OBTAIN A VOM!

Sure, I'll be glad to, and I'll post the results here. Your next-to-last post confused me, is all. You seemed to be faulting the fixture no matter what—and I'd already tried it elsewhere and found it OK.

nealtw > ...Are there any red wires anywhere in this system? and if you have power at the light box, does it go away when the switch is turned off. And how many switches are in the switch box?

No red wires anywhere... Yes, I can switch the power at the light box on and off... There are 3 switches in the light box:

_ Two 2-pole rockers

_ A CFL-compatible dimmer (for our living room). As it has a ground terminal too, I've connected that to the box's ground screw (which is connected to an uninsulated ground wire). BTW, I did try removing this dimmer but it didn't help.

Thanks for your ongoing help w/this. BTW here in the 'burbs this qualifies as real excitement. :?)

Hey Joe: I guess I'm not the only one that screws up that black and white in the switch loop. The only thing I can come up with is a broken wire leading to the switch and may still have intermetten connection. I would do a close inspection of those wires near where they are clamped in the back of the box. AL. dosn't like being handled to much and that is where the trouble started. You may be able to loosen the clamp and pull a few inches more.

Zepper: what have you found?

Hi guys,

My friend the (real) electrician was here today. Turned out we had a melted connection under the sink at the junction box for the dishwasher and garburator, and for some reason the breaker hadn't blown. This caused a voltage leak that played major weirdness with other circuits as well. (For example, the mysterious porch light box was getting only 75v.)

Everything's fixed now, and I'll be replacing our entire set of breakers. My friend said our old Westinghouse breakers aren't made anymore because they were so unreliable.

Thanks for your theories and input. Cheers, Z.

This is a good write up about AL. wiring

http://www.halifax.ca/Fire/AluminumCopperWireBasics.html

zepper said:

I just thought you guru-types might have a clue. If you don't, please don't feel obligated to put me down, as my wife is already handling that task nicely.

Click to expand...

So how did you fudge the voltage test that you claimed was good?