How do I replace 2 wire timer with a 4 wire timer?

Old 04-08-12, 01:12 PM
Thread Starter
Join Date: Apr 2012
Posts: 1
Received 0 Votes on 0 Posts
Unhappy How do I replace 2 wire timer with a 4 wire timer?

I have a two toggle light switch in one box in my entryway. One "side" controls the interior light. The other "side" was a timer controlling the porch light only. The two were completely independent. The old timer had 2 black wires only. One black wire coming out of the wall was connected to one black on the timer. A white and a black wire from the wall were both connected to the other black wire on the timer. There was a little black wire making some sort of bridge in there. There was a copper wire from the wall loose. The new timer has 4 wires - black, white, red and green. The instructions say to connect white to white, black to black, black to red and green to a screw on the metal box or cap it if no metal box. I have done this exactly, and I either have no power at all to the light toggle or the timer, or if I switch the 2 black wires between the red and black I must then flip the interior light switch "on" to to get power to the timer. What am I doing wrong?
Old 04-08-12, 02:31 PM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,964
Received 9 Votes on 8 Posts
Welcome to the forums! Not sure of your installation, but your new timer will probably need a neutral, not just a "white" wire. The white wire that is attached to one side of the switch is most likely part of a switch loop and not a neutral. Would there be a way for you to remove the power from the lights, pull the switches from the box and show us the wiring to them? It would certainly help for us to see what you see.
Old 04-08-12, 09:25 PM
Nashkat1's Avatar
Join Date: Mar 2012
Location: USA
Posts: 8,469
Received 5 Votes on 4 Posts
Hi mamalasagna. Since you haven't posted pictures, here's what I'm envisioning. It sounds like you have a 2-gang wall box with three 2-wire cables coming into it. Each of the 2-wire cables actually has three wires in it: a black, a white, and a bare copper. The black wires are the "hot" wires, the white wires are the "neutrals," and the bare copper wires are the grounds.

I'm also guessing that the wires on your new four-wire timer are a "feed-in" - the black, a "feed-out" - the red, a "neutral" - the white, and a "ground" - the green. A careful reading of the paperwork that came with the timer, and/or reading markings near each wire on the timer - if those exist - should confirm this.

So, if I'm correct, one of your three cables is the "feed-in," which brings the power from the panel. One is the "feed-out" for your interior light and the third is the "feed -out" for your porch light.

If so, what you need to do to have everything work the way you want it to is to splice all of the ground wires together and add the green wire from your new timer into that splice. Splice all of the neutral wires together and add the white wire from your new timer into that splice. Connect the black wire from the feed-in cable to one terminal on the toggle switch for your interior lights and to the black wire on your new timer. Connect the black wire that feeds your interior light to the other terminal on the toggle switch. Connect the black wire that feeds your porch light to the red wire on your timer.

Let us know how it works out, please.

Thread Tools
Search this Thread
Ask a Question
Question Title:
Your question will be posted in: