I purchased an Intermatic Model EJ500 Self Adjusting Indoor Wall Switch Timer. I want to use the timer to automate my front porch lights. The switch I am replacing is one of three 3-way switches that control the lights and is in the middle of the circuit.

I have two sets of wires coming to the current switch. There are two red and two black wires that connect to either side of the 3-way switch (one black and one red on each side) and two white wires that connect to each other but not the switch.

The instructions say to locate the common wire and connect the black wire from the timer to the common wire. What are my common wires? Then the instructions say to connect the other two wires from the timer, one blue and one red, to the other wires coming out that are not the "common" wire. Please help.

Also, I assume I am going to have to install a jumper cable on the other two 3-way switches so any help you can give me on that would be appreciated. Do I need to install jumpers on both of the other 3-way's or just one of them?

The switch that you are working with is a 4-way switch. Four way switches are used in between two 3-way switches, giving you three or more points to turn lights on and off. A 3-way switch will have 3 wires connected to it. The common screw will be marked or will be a different color, usually darker. You'll have to locate your timer at one of the other switches

Common is the white or neutral, and connects to timer common(neutral), You will want to eleminate the 3 and 4 ways(jumper)so timer will always be operating, you can install switch at any of the locations.
The red may be line(constant hot)and blue may be load(to light)

Strat, in this case the common is not the neutral and is not necessarily white, it is the "common" of a 3-way switch. A 3-way switch having one "common" and two travelers.

The OP certainly does have 4-way switch there, meaning there are three or more switching locations. I am not sure if this timer can be used in place of a 4-way. I do know it can be used in place of a 3-way.

Stan, I don't think this is a 3 or 4 way timer?
I was thinking he was talking about timer that has a Common(neutral), a red and a blue(line and load).
You don't want to put timers on 3 or 4 way, unless for on or off override.

I do know those Intermatic in-wall timers include a little jumper so then can be wired into an existing 3-way setup.
The jumper gets placed on the other 3-way switch.

If I read the original post correctly then he he wants to replace the 4-way switch in the circuit with this timer. According to the instructions I found online this can't be done easily. It will have to replace one of the 3-way switches and the 4-way be replaced by a 3-way. Also an additional wire is required. Here's the instruction link in case anybody can see any easy way to do it http://www.intermatic.com/images/ins...158ej11853.pdf

The easiest way I see to make use of this timer is to remove the 4-way switch altogether by connecting the 2 blacks together and the 2 reds together and leaving the whites connected, then putting a blank cover over the box. Then put the timer on one of the 3-way switches by following the instructions. But that eliminates one of your switch locations and may or may not be a safety issue depending on where the removed switch was located.

Why bother removing a switch? The timer is not something you need to go to very often, so putting it in place of one of the 3-ways should not really be an issue, should it?

Removing the 4-way switch would seem to be easier than adding additional wiring, which is required if 3 switch locations are to be retained. At least that is how I read the instructions. The manufacturers instructions are linked in my previous post.