I'm having an odd problem with a lighting circuit. 3 sets of lights are on this circuit:

1) Exterior lights, always on (CFL)
2) Kitchen lights on a 3-way circuit, 6 cans & 2 CFLs over the island
3) Accent circuit, halogen pucks via switched receptacles

Occassionally, when switching on the kitchen lights, the lights will come on for a moment, then the whole circuit (including exterior and puck lights) goes dead. The breaker does NOT trip, but if the breaker is reset, the lights will come back on. Sometimes they will blink again and go out, other times the lights will come on as normal and stay on.

This circuit has a cable going from the breaker panel to a 4x4 box with the first kitchen 3-way; the wires are nutted & pigtailed in here and then go to the 2x4 box for the puck switch where they're nutted & pigtailed again. All cabling is NM. This first box is only about 3' from the panel, which is 2 stud-bays over on the opposite site of the wall, in the garage.

1) This circuit was installed 18 months ago during construction of the addition; the problems started about 1 month ago. Right about the time it got really cold, but also coinciding with increased activity in the room above the kitchen (the room above the kitchen was only finished 2 months ago).
2) Happens whether the pucks are on or off
3) Replaced breaker, still occurs
4) Inspected and remade the first wirenuts in the first box, the only splice common to the whole circuit. The L & N nuts were tight, and with no indication of arcing. The ground was also securely bonded.
4) Unscrewing two CFLs from the kitchen seemed to reduce symptoms, but not eliminate them.
5) Problems never observed when kitchen lights are off, only when the kitchen lights are turned on.

What might be causing this? I'm at a loss for what to check next. I'll leave the panel cover off the next few days to check for a high-impedance fault or open neutral if it occurs again, but that's about all I can think to do. Loose neutral in the panel maybe?

It is time to get out your meter and figure out where the last place you have power is in the failing condition.

Did you take a good look at the stab under the breaker?

Could it be a possible break in the Hot? (nail through the cable or pinched under a floor board above) When the circuit gets extra load the connection breaks. Is it possible that you could temporarily bypass the cable in the walls to eliminate which run could have a break, ie run power from the panel to the 4x4 box.

With all the analysis you've done, I'm surprised you didn't check it.
All it takes is a screwdriver, and less than 30 seconds.

Did you wire it yourself? I had a similar issue some years ago and discovered that someone had picked up power from an attic fan. The t-stat would turn the lights on and off when the weather warmed up and the problem would get worse in cooler weather. Drove me nuts.

electure, I didn't think to check the neutral when I had the panel open; from the symptoms, I was absolutely convinced it was just a faulty breaker and replacing it would fix the issue.

Greg, yes, I wired it myself. I can see how your thermostat would cause issues, lol...

Thanks everyone- I'll check it later today and let you know how it goes. Man, I hope it's just a loose screw on the neutral bar, that's such an easy fix... If that fails, I'll throw the multimeter everywhere I can and jumper over that first leg of cable if anything points to damage.

If the neutral looks OK, how about double checking the breaker seating on the bus. Sounds a little too easy, but I've found that to be the little bugger in a similar situation once before.

Burned or mis-shapen stabber could be one possibility.

Good Luck!

I would check the bus where the breaker plugs on. I just repaired one that had the lights blinking and slowly going brown and then back to full on. Found a bad connection on the panel bus, same as yours breaker would not trip but you could reset it and cure the trouble for a while, sometimes. Breaker showed no arc markings, bus had slight markings visible only under bright light. You never would have convinced me that was the trouble if I had not been there.

It was the freaking neutral. Opened the panel, traced the hot down from the breaker- started tracing the neutral up and immediately heard it sizzle. It wasn't just loose, I'd never even given the screw the first turn. ARRRGHHH! I'd even gone through that panel a month after it was installed and torqued every single screw and STILL missed it.

Ah well, I suppose the good news is that my house hasn't burned down and it was easy enough to snip off the damage a pick a new slot on the bus bar.

"Occassionally, when switching on the kitchen lights, the lights will come on for a moment, then the whole circuit (including exterior and puck lights) goes dead. The breaker does NOT trip, but if the breaker is reset, the lights will come back on. Sometimes they will blink again and go out, other times the lights will come on as normal and stay on. "

"It was the freaking neutral. Opened the panel, traced the hot down from the breaker- started tracing the neutral up and immediately heard it sizzle. It wasn't just loose, I'd never even given the screw the first turn."

Now that you found it and corrected it, I can easily see that the vibration from resetting the breaker would rattle things just enough to make the neutral connection connect again for a while. So it's very likely that you solved this mystery. Things like this are what troubleshooting is about...

Spring tension of the wire likely held it in contact the first year or so. But slowly, vibration created small arcs which scored the surface and dirtied it, which had a snowball effect until it got to the point where it would quickly fail.

Oddly, while resetting the breaker had an effect, pounding on the panel with my fist didn't