enter image description hereUpgraded a dimmer to be compatible with future LED lights. The old was a three way dimmer but it had no ground wire and no markings. I BELIEVE I found the common and wired this to the appropriately marked wire to the new dimmer. But the other two wires I was unsure of and just wired them to the red and red/white of the new dimmer. I also grounded the receptacle to the spare copper wire sitting in the box. Turned on the breaker and everything worked fine at that dimmer controlling the lights. The other switch appropriately turned the lights on and off. BUT when I tried turning on other lights ON THE SAME CIRCUIT. The breaker IMMEDIATELY tripped. What did I do wrong?

Okay. I added the picture. Let me detail. There are 2 sets of 3 pair wire and 1 4 pair wire. All the grounds are pigtailed together with the ground wire shown. All of the neutrals (3 of em) are tied together to the left in the picture. Moving CLOCKWISE. The black wire with the yellow wire nut(its just capped off for a little safety) is tied to the the next wire nut RED which has the black from the 2 sets of the 3 wire.(I am assuming that's the common and wired the dimmer black to that). The next wire with the yellow wire nut at about 5 o'clock is one of the travelers to the 4 wire and finally the red wire is the other traveler.

Now here is where it gets very interesting. I took the dimmer out and capped off everything as shown. When I flip that other switch (which presumably and physically appears to control other lights on the same circuit) it STILL POPS the breaker instantly. So what gives? Happenstance that that switch happens to be faulty?(we are painting the house)

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    We are thankful you took a picture of the old wiring (not)
    – Traveler
    Commented Jul 23, 2023 at 3:29
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    Need pictures showing all the wiring. No "common" in typical AC wiring - did you mean neutral? Neutral is (almost) always white, white is not always neutral. 3-way wiring in particular can result in unexpected usage of white wires. Commented Jul 23, 2023 at 3:29
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    @manassehkatz common is the correct name for the black terminal on a 3-way. The problem is the old 3-way was a dimmer. It should have been rolled back to plain 3-way before anything was attempted. Also there are no spare wires in boxes, a bundle of grounds must not be broken up, your ground must be added to it while keeping them together. Commented Jul 23, 2023 at 5:50
  • Yes, "common" is the name for the black terminal on a 3-way. But really it is in the end either "always hot" or "switched hot", depending on the 3-way wiring scheme and the location of the switch. Based on the phrasing, I'm not so sure that's what is going on or if "common" here is used as another name for neutral. Commented Jul 23, 2023 at 13:50
  • I updated the original post(with detail about the picture and what I have now done) and added a picture Commented Jul 23, 2023 at 15:12

1 Answer 1


the other two wires I was unsure of and just wired them

Stop what you're doing and make sure the circuit is off.

Remove the switch(es) that you replaced.

Get a multi-tester and identify every wire.

If necessary, turn on the circuit and probe the wires to determine which is hot.

If necessary, take down the lights and identify the switched hot wire.

Only after identifying all 4 wires for each switch, then it is safe to install them.

capped off everything as shown... STILL POPS the breaker instantly. So what gives?

The circuit breaker is intervening to stop you from melting the system.

The red wire nuts are existing. Untouched

Based on that comment, there may be an unrelated problem on the circuit. If the only thing you changed was with those 3 other wires that are now safely capped then you should leave them capped and troubleshoot the switch that's tripping the circuit.

  • I would strongly recommend against the OP removing any existing switches they didn't touch previously. Preserving any remaining existing (presumably functioning) wiring is a priority after messing up the 1sr install.
    – brhans
    Commented Jul 23, 2023 at 15:46
  • I thought both switches were replaced. I may have misinterpreted that part or it wasn't clear. The question has since changed anyway. Answer updated. Commented Jul 23, 2023 at 16:29
  • The "other switch" on the 3 way leg was not touched. Only the dimmer. And no other switches were touched on the circuit. Even the one that trips the breaker instantly. Commented Jul 23, 2023 at 21:18
  • The red wire nuts are existing. Untouched. Commented Jul 23, 2023 at 21:41
  • @Northernlights Thank you for clarifying. Had you mentioned that in the original question this would have been easier to understand. My answer is updated. Commented Jul 23, 2023 at 22:46

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