DIY Message Boards
Replacing standard switch with timer switch

This topic can be found at:

Nov 08, 2013, 10:17 PM
Dan Miller
Replacing standard switch with timer switch
This will, hands down, be the dumbest question you've seen in awhile. I own that. :-)

We have a standard wall switch that turns on our exterior flood lights at night. I would like to replace it with a timer switch that I have purchased.

The standard wall switch has three wires. Sadly, I have no idea what color the wires are because they are completely painted over. Two look black and one looks copper and is screwed into what looks like a grounding screw to me.

The timer switch has four wires. Red, Black, White and Green.

Am I out of look with this configuration because I'm short a wire? What am I missing?

Nov 09, 2013, 08:54 AM
Not really a stupid question. Believe me we've had much worse.

Is there a group of wires in the box that are connected together with a wirenut? These should be white. A regular switch does not need to be connected to the white (neutral) wire but your timer does because it needs power to run. It is possible that you don't have the white wires wirenutted together because you have a switch leg line to the light with the power coming in at the light instead of at the switch.

Here is a diagram of a switch leg with the power coming in at the light. http://www.electrical-online.c...-switch-variation-1/

Here is one with the power coming in at the switch.

If your switch is wired like example number 1 you won't be able to easily put in your timer. If it is wired like the second diagram you need to tap into the white wire to give your timer switch a neutral. This will involve adding a pig tail to the white wires and possibly using a larger wirenut.

General Disclaimer

Any advice given here is general in nature and is not necessarily valid for your given area. If in doubt check with your local codes enforcement department for what is required when doing electrical, plumbing or structural work on your house. Permits may or may not be required in your area and home owners may not be able to DIY some tasks. I have no way of knowing if you have the skills needed to complete the tasks you are asking about, when in doubt seek professional assistance.

My advice may be worth exactly what you pay me for it. :-) For the record I did not stay in a Holiday Inn Express last night.