I wanted to replace a dimmer switch on a wall outlet that had 3 switches next to each other. The dimmer was in the middle. There were 3 wires I disconnected from the old switch - green for the ground, a red wire T'd with wire nut with a black wire attached, and a black wire T'd with wire nut with a black wire attached. The dimmer I bought had no wires attached only color labels to tell u where which wire is suppose to go. I put the black wire from the wall to the black label on the dimmer. I put the other wire (red) to the yellow label on the dimmer. Green to green. When I turned on the power and tried the light the fixture to the left shorted out. What did I do wrong? enter image description here

  • 1
    Is the photo of the old dimmer, or the new one?
    – Tester101
    Jan 12, 2015 at 11:18

3 Answers 3


I can't be certain what you've actually done here but I do know what you have there, whether it's the new or old one, is a 3-way dimmer. Sounds like it'd be the new one because the old one doesn't sound like it was wired as a 3-way is done having only 3 wires (g,r, blk).

A grounded 3-way switch has 4 wires: a ground, a feed from the source or return to the light, and two travelers. What you had originally doesn't look like a good fit for the new one.

Why is it shorting out? Could be a number of reasons. But you'll probably have to clarify what you mean by the fixture to the left as we have no clue of where/what that is. It's most likely either the way you've wired it or contact between metal parts and wires in the box seeing as it looks pretty full. It may not be anything you've changed as far as the wiring and may be the shifting of the wires. Perhaps the bare ground is now sitting on a wire that has a bit of wire exposed out of the wire nut.

A couple things you could try:

  1. If you're installing a device in a packed box, put a wrap of electrical tape around the back side covering the terminal screws.

  2. Use a continuity tester to see if you have some unwanted contact between the ground/neutral/hot, or metal.

In the end, if I'm correct in assuming you have the wrong type of switch, I'd return it for the correct one, it should be cheaper and then it will be a correct match.

  • How can a dimmer with only two connection points (ignoring the ground) be a 3-way dimmer? Jan 12, 2015 at 19:32
  • @SpeedyPetey, well to be fair the connections are not shown in the pic; we're looking at the opposite side. But if you'd like to confirm my belief, simply zoom in close. You'll see "1 pole/ 3-way Dimmer" on the label. You'll also be able to see there are 2 "yellow" terminals. Jan 12, 2015 at 19:40

If the switch on the left shorted out you must have made the bare ground touch one of the screws on the switch.

Is it safe to assume you tried it with the dimmer hanging out as in the picture?


look at instructions carefully. one wire goes to "line" (main power) and and another to "load" ---this goes to the fixture. the way you tell is switch the fixtures to "OFF". when the lines in the the box are exposed use a hand held current detector (Klein makes a good one), the wire that has power will beep and blink red, the load will stay green (no current). carefully put switch on, then the load line will now beep and blink red.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.