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Electrical Wire and Cable

Wiring a Time Switch for a Outside Light Fixture

By Dave Rongey - Summary:

How can I replace a wall switch with a time switch for my outside lights? How to Wire a Timer Switch for Outdoor Lights, The Most Common Wire Colors and Connections for a Time Switch and How to Connect Them.

Wiring a Time Switch

Electrical Question: How can I replace a wall switch with a time switch for my outside lights?

This electrical wiring question came from: Susan.

Dave’s Reply:
Thanks for your electric wiring question Susan.

How to Wire a Timer Switch for Outdoor Lights

Application: Wire a Time Switch to Control Outside Lights.
Skill Level: Beginner to Intermediate – Best performed by a licensed electrician.
Tools Required: Basic Electricians Pouch Hand Tools and Voltage Tester.
Estimated Time: Depends on personal level experience and ability to work with tools.
Precaution: Identify the light circuit, turn it OFF and Tag it with a Note before working with the wiring.
Notice: Installing additional fixture wiring should be done according to local and national electrical codes with a permit and be inspected.
Materials: Make sure the replacement light switch has the same amperage and voltage rating as the original switch, and is fully compatible with the electrical circuit, the light fixture and the type of light bulbs being used.

Time Switch Wiring Connections

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4 Responses to “Wiring a Time Switch for a Outside Light Fixture”
  1. Dave Rongey says:

    Hi John,
    You will need to identify the existing light switch, which sounds like it may be a 3-way switch that works with another 3-way switch in another location of the home. If the existing switch is in fact a 3-way switch then you could not use the automatic control switch without modifying the wiring of the existing 3-way switches. The modification would include identifying the line wire of the circuit power and the load wire that leads to the light fixtures. The electric wiring of each of the 3-way switches may need to be examined because there are several ways to wire 3-way switches, but it all translates back to identifying the wires of the Line and the Load. After completing that stage of the process you may want to remove the second 3-way switch, cap off any unused wires, and place a blank cover onto the box, or just leave the switch in place, but understand that it will not be operational if the modification has been successfully achieved. the only wire left in this scenario would be the ground wire which is the green or bare copper wire.
    I hope this helps,

  2. JOHN says:

    I want to replace the outside light switch with one that turns lights Off and On automatically. The existing switch has a copper wire connected to the switch frame. two other wires connect to the switch, one above the other. A fourth wire connects to the bottom of the switch on the other side opposite the copper wire. The new timer only has three wires. Of course the wires coming from the box are all black except for the copper ground. The new switch wires are labeled green-black-blue for ground-line-load respectively. How do I know which 3 wires off the old switch to use?

  3. Dave Rongey says:

    Hi Robert,
    The typical electric wire connections for a time switch are the following:
    White wire – connects to the circuit neutral.
    Black wire – connects to the circuit power.
    Red wire – connects to the light fixture to be controlled by the time switch.
    So – as you can see, the timer switch that you have requires a separate neutral wire, and from what you have described, the light switch that you have does not have a neutral wire, so the time switch will not work for that location. A standard switch with only two wires is a switched leg which is the white wire, and the power source which is the black wire. There are a few time switches that do not require a separate neutral wire, however they will only work with light fixtures that have incandescent or quartz lamps. If this describes the type of light fixtures that you have then you may want to locate a time switch that does not require a neutral wire.
    I hope this helps,

  4. Robert Derenzo says:

    I want to replace a light switch for an outside light fixture with a wall timer. The timer has a white, black, red, and green wires. Inside the electrical box there are white, black and green wires. What do I do with the red wire coming out of the timer?