How to Install a Programmable Timer Switch

By: Julie Day
Timer switch on wall next to porch light

Programmable timer used to control a porch light

In-wall timers can turn a standard wall light switch into a programmable timer complete with 7-day customization, random vacation settings, and a backup battery.

I use the timer to control the porch light over the kitchen door, so there’s no more coming home to a dark house at night or leaving the light on all night be mistake.

Features of In-Wall Programmable Timers

  • Automate Functions: In-wall timers can automate lights, fans, pumps, or anything else that can be controlled by a regular light switch.
  • Save Energy: By programming the timer to come on only when needed, you can save energy without having to think or worry about it.
  • Timer switch showing programmable interface

    Programmable timer interface

  • Fully Programmable: Using the 7-day program cycle allows you to set the timer according to your schedule. Many also have a “random” setting to provide irregular security lighting when you’re away on vacation.
  • Manual Override: Need more light? You can override the settings with the touch of a finger, and it’ll return to the program in the next cycle.
  • Backup Battery: The integrated NiCd rechargeable battery prevents your settings from being erased during a power outage.
  • Standard Size: In-wall timers fit inside a regular wall switch box. They come with a cover plate but will also accept standard square cover plates.

How to Install a Programmable In-Wall Timer

    Turning off a circuit breaker

    Turn off power at circuit breaker

  1. Choose Proper Switch: Make sure the timer is rated for the same amperage as your existing wiring. A 15-amp timer will replace most standard light switches.
  2. Turn Off Power: Turn off the circuit breaker or unscrew the fuse that controls the wall switch and fixture.
  3. Remove Switch Cover Plate: Remove the cover plate and use an electrical tester to verify that the power is off.
  4. Unscrew Existing Switch: Remove the screws holding the existing switch in the box, and pull it out, leaving the wires attached.
  5. Removing screws on existing switch

    Unscrew existing switch

  6. Inspect Wiring: Before disconnecting the old switch, compare the wiring with the instructions for your new switch. The timer wiring should be similar to your old switch, but the wires aren’t always an exact match, and it can be easy to get confused once everything is disconnected. The new switch should have instructions for different types and ages of wiring systems.
  7. Remove Switch Wires: Disconnect the electrical wires from the old switch and remove it.
  8. Using wire nuts to attach wires to timer switch

    Attach wires to timer switch

  9. Attach Timer Switch Wires: Attach the electrical wires to the timer switch, following the instructions and wiring diagram that came with it. If the ends on the wires are worn, cut them off and strip them the insulation of the ends for a fresh connection. The wires may attach directly to the switch with screws or the switch may have short pigtail wires that are joined to the existing wiring using wire nuts (wrap wires together and turn wire nuts clockwise to tighten). If your house doesn’t have a ground wire, follow the instructions to properly ground the switch.
  10. Inserting timer switch into electrical box

    Insert timer switch into box

  11. Attach Timer Switch: Arrange the wires so they fit in the electrical box. Push the timer switch into the box so the flanges on the switch are flush with the wall and aligned with the screw holes in the electrical box. If the box is metal, be sure any exposed switch terminals are not touching the box. Screw the switch to the box with the provided screws. Attach the cover plate, and screw it in place.
  12. Turn On Power: Turn the power back on by flipping the circuit breaker on or screwing in the fuse.
  13. Attaching cover plate to timer switch

    Attach cover plate to timer switch

  14. Test Switch: Turn the timer switch on and off to make sure it is working properly using the manual switch control. This is often done by pressing on the access panel on the front of the switch.
  15. Program Timer Switch: Now comes the fun part – programming your timer! Grab a magnifying glass (or prepare to squint), since the buttons and LCD screen are tiny and can be hard to read. Follow the instructions to set up your timer according to your schedule. Start by learning how to set the clock, then proceed to assigning settings to each day of the week.

Further Information


Please Leave a Comment

17 Comments on “How to Install a Programmable Timer Switch”

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  • David L Says:
    November 21st, 2017 at 8:33 am

    I have a light on my garage that is hard-wired to the breaker panel – there are no switches to turn it on/off, and that breaker also controls the 2 garage doors. I’d like to install a programmable timer on the light to have it on for a couple hours in the evening, maybe the early morning when we leave for work.

    I imagine I need to separate the garage doors to their own breaker, then install an in-line timer on the power going to the light?

  • Gary Grove Says:
    June 24th, 2017 at 2:23 pm

    How do I identify the load wire from the line wire? I have 3 black wires connected to the old switch. one at top and two at bottom.

  • Trevor Says:
    December 21st, 2015 at 12:17 pm


    I have a 1 RPM egg turner motor and I just bought a timer (Inkbird Digital Twin Timer Relay Time Delay Relay Switch 110-220V Black IDT-E2RH ) so that I could turn power on for 30 seconds to roll the eggs 180 degrees and off for 6 hours then repeat the cycle. What I need help with is the termination wiring arrangement.

  • Official Comment:

    Ben Erickson Says:
    November 13th, 2015 at 8:10 am

    Hi Lou,
    You can find a PDF of the GE programmable wall timer (model 15312) on the Home Depot site at

  • Lou Dio Says:
    November 12th, 2015 at 7:52 pm

    Lost instructions for my GE programable wall timer model#15312. Hope you can help. Thanks

  • tina Says:
    October 16th, 2015 at 9:51 am

    I need instructions on how to reset the programmable timer for my front porch lights. I have instructions but they are in minute print and can’t read it. I want to reset from turn on 5pm to 6pm. also my lights blink when turned off. Why is that? Thanks, hope you can help.

  • Louie Says:
    August 21st, 2015 at 1:45 pm

    Can I install a westek digital wall switch timer to replace a 2 wire standard switch? There is a 3 way switch in same box.

  • Jimboo Says:
    April 2nd, 2015 at 11:48 am

    The red wire is likely to add additional lights to the same timer.

  • Trina Says:
    June 10th, 2014 at 5:48 pm

    I’m curious about the red wire…where did you attach it?

  • Justin Says:
    November 24th, 2013 at 7:51 pm

    I have a switch in my house that controls about 5 lights outside (just pathway and spot lights). I wanted to install a timer so that they can come on a few hours a night and off automatically.

    I went to Home Depot, bought an inwall timer, when I opened the old switch, it has only a black and white wire and looks to be ‘end of circuit.’ There are only wires coming in, no wires going out to the wall to another junction, etc.

    The timer did not work (it did power on and off but the lights would not turn on outside, I belivee cause there is no neutral)

    can I put a timer switch in this? Are there ones made for end of circuit?

  • Confounded Says:
    August 9th, 2013 at 5:47 pm

    If your house doesn’t have a ground wire, follow the instructions to properly ground the switch. Where could I find these instructions?

  • Holly Says:
    September 13th, 2012 at 9:58 am

    My uncle tried to install one of these switches, but all it does is blink off and on. We tried new batteries and reprogramming, and it only blinks. Could this be happening because there are two switches for the same light? (We have one switch at the front door and another in the garage that operate the front outdoor lights) …. so any ideas?

  • Carissa Says:
    January 6th, 2012 at 10:46 am

    I have been looking at installing some timer switches. The unit I have chosen is compatible with CFLs, which is what I plan to use, and also says that it requires a neutral wire to be used.

    When I remove my switch plate and pull the switches out, I can see that the switches each currently have 2 black wires (live and load) and a ground wire attached to them. There are 4 bundles of wires that come into the box – each has a black, white, and bare copper wire in it, and one also has a red wire. All 4 of the white (neutral) wires are twisted together and capped with a wire nut. The ground wires that are not run to the switches are also twisted together and capped with a wire nut (somehow there must be some additional ground wires in the box than what I saw because there are 2 attached to the switches and 4 more twisted together). The red wire does not actually have any wire exposed, nor is it attached to anything.

    I am thinking that I would need to find the neutral wire that belongs to the same bundle as the two black wires attached to the switch and use those 3 to attach to the new switch, and then take the ground wire that was attached to the current switch and twist it in with the other ground wires and re-cap it with the wire nut.

    But I don’t know if this is the right way to do things (I am no electrician!) and I don’t want to do something unsafe.

    From my description, is there any way you can tell me whether what I’ve described sounds right? I truly appreciate it!

  • Ganeson.D Says:
    March 21st, 2011 at 8:47 pm

    How do you connect a programmable timer to the circuit to control few light without removing the light existing switchs. Please, could you show in a drawing?

    Thank you.

  • Official Comment:

    Julie Day Says:
    January 11th, 2011 at 9:13 am

    Jan, I haven’t had any problems with the batteries – that sounds frustrating. I’d try a different brand of timer to rule out the unit itself, and if it still doesn’t work I’d probably call an electrician to look over both the installation and the wiring circuit to try to figure it out. You might be able to return the old timer in exchange for a new one if you explain to the store what’s happening.

  • Official Comment:

    Ben Erickson Says:
    January 11th, 2011 at 9:45 am

    Hi Jan,
    If your timer hardwired as Julie’s is in her article above, your battery should only be needed if the power goes off (as a backup to save your settings). Since her’s is rechargeable, the power from your house should keep it charged up and it should last for years. If your timer is wireless and requires battery power to work, then if might burn through batteries faster, but I would still think it would last quite a while.

  • Jan H Says:
    January 11th, 2011 at 12:03 am

    Love programmable 7-day digital timers, but we are having a problem with the battery in the timer wearing out every 30 days. That can’t be normal, and we are stumped as to what might be wrong. Incorrect installation? Bad timer unit? Have you run into this problem with these timers?

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How to Install a Programmable Timer Switch