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2 three way switches control two cfl fixtures (2x13W) in stairwell. 1 Switch and light at top and 1 of each at bottom.

Power(black) into to Switch 1, then Red and Black to Switch 2, then black to Light 1, then White continues on to Light 2 via Switch 2 box, and back to Neutral from panel at Switch 1.

Removing light 1 from circuit stops light 2 from flickering.

Voltage measured across Switch 2, hot wire to Common (black to Light 1), is 120V when open (off), and ~20V when closed (on).

Lights are in series, is this my problem?

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The lights should be hooked up in parallel, not in series.

  • Instinctively that makes sense...except how is any current making it to the 2nd bulb if the first one is removed? – manassehkatz-Reinstate Monica Sep 24 '19 at 2:00
  • I’m re-connecting the 2nd light as if the first light didn’t exist. From Switch 2 the common connects to white, which returns to light 2. – aboynamedcolin Sep 24 '19 at 2:06
  • I hoped this was not the case. The original wiring used another circuit’s neutral on light 1 to solve this. – aboynamedcolin Sep 24 '19 at 2:09
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    @aboynamedcolin Except for "christmas tree lights" (and not even all of those), lights are normally wired parallel - otherwise one bulb goes out and you're in the dark. In addition, while with incandescent it makes little difference serial vs. parallel, with fluorescent & LEDs it can make a big difference. – manassehkatz-Reinstate Monica Sep 24 '19 at 2:11
  • @ manassehkatz I took the OP's statement that he removed the light, not bulb, to mean fixture and would then just connect the wires. – JACK Sep 24 '19 at 12:04
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You've made a circle. That's not allowed in AC power, and for good reason.

The white wire is spare from SW1 - SW2 - L2. You need to use that for neutral instead of having the white shortcut from L1 to SW1. Yes, that means the white "doubles back" physically and travels 3 sides of a square.

The operating principle is Currents should be equal and opposite in each cable or conduit. No loops; tree topology only. If hot goes up a branch, neutral must come back that branch.

In other words wiring should be (if straightened out)

             /-----y-----\
            /             \
SUP---b---SW1------y------SW2----r-----L2-----r-----L1
  \                                    |           /
   \--w----+-------w-------+-----w-----+------w---/     

 b = Always-hot 
 w = True Neutral (must be white)
 y = Travelers  (will be black or red; remark them yellow)
 r = Switched-hot  (will be black; remark red)

Fix that first because it's impossible to even diagnose the other problem while this problem is so broken.

If you have been wiring with individual wires somehow, stop doing that. Individual wires aren't listed for direct use.

If you follow my color advice, things get a whole lot easier, especially if 3-way circuits are involved, which (without wire remarking) are confusing on a good day.

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Doesn't sound like the lights are wired in series. Are your neutrals connected to both lights by pigtails and spliced together in both switch boxes? If not, any voltage on the neutral might be interfering with getting proper voltage across the bulb.

Otherwise I'd check all connections for good, clean contact and tightness by removing and retightening all wire nuts.

I've had it happen to me where trying to get 3 #12 wires into a yellow wire nut (which is supposed to handle that) actually pushed one of the wires back just enough that it barely made contact with the others. This lead to one outlet in the middle of a wall not working consistently, but all the others were fine. Took half an hour to figure out, half a minute to fix.

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