enter image description here

So i'm trying to replace the exterior light switch to a timer switch.

On the same switch panel, there are two other switches which control the ceiling lights in the hallway. The dimmer in the center is just a single switch, and the one to the right is a three way switch for another sets of pot lights.

SO the one I'd like to replace is the one on the left. The image at the bottom is how I connect the timer but does not work ...

any suggestions??

  • When you say "but does not work", what exactly do you mean? How is it not working? Do the lights not turn on, do they always stay on, etc.? In the original diagram the ungrounded conductor from the third cable from the left was connected to the switch, where does that go, and why did you wire it straight to power?
    – Tester101
    Mar 16, 2015 at 10:09
  • The original is what was there when I opened the panel. the 3rd black wire connects to the first switch is for the dimmer switch(in the middle) for a separate light. doesn't work = nothing for exterior lights, dimmer switch controlled light has no power, the light on the 3 way switch seems ok.
    – lee
    Mar 16, 2015 at 18:55
  • It seems like there's too many wires attached to the first switch in the original wiring.
    – Tester101
    Mar 16, 2015 at 19:42
  • Suggestion: Consider a photocell instead of a timer. Timers get screwed up by seasonal changes in sunrise/sunset and by power outages. Photocells respond to actual dark/light conditions. Feb 3, 2020 at 13:47

1 Answer 1


We start by numbering the cables in your diagram from left to right:

  1. is an always-hot feed backstabbed into the single pole switch (it's always hot because it's backstabbed at the same end of the switch as the incoming hot feed).
  2. is another always-hot feed (were I to guess, this is the circuit coming in, but there's an off chance some dunderhead wired it to come in on cable #1 instead). I can tell because of how it's double-looped at the switch terminal screw then pigtailed off to the rest of the switches.
  3. is the outbound switched hot from the single pole switch to whatever lighting is on it. (It is connected to the other end of the switch from the hot terminal.)
  4. is the outbound dimmed hot to its corresponding lighting load.
  5. and 6. are the curious cases -- you'd expect both travelers to be in 6. but perhaps the two cables are run together as part of the same circuit in a California 3-way configuration? (The traveler terminals on a 3-way switch are both at the same end.) Either way, they're irrelevant to your timer trouble.

From here, we can tell where your error is -- you wired the switched hot on the timer to cable #1's hot, when the original single pole switch was switching cable #3's hot.

So, turn off the power to the circuit, then unnut the hot (black) and switched (red) wires on the timer, and unwind the switched wire from cable #1's hot and cable #3's hot from the pigtail junction. Then use new wirenuts to nut cable #1's hot into the pigtail junction and cable #3's hot to the switched wire from the timer. Put everything back together, turn it back on, and enjoy your new timer!


Your Answer

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

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