Switch wiring Need connections for switch wiring - 3 pair connecting to motherboard

remember the colored wire is +, the + and - should be printed very small on the board near the connectors as well as what they are example (HDLED is hard drive LED) or (PWRLED is power LED) or (PWRSW is power switch) these are examples yours may differ slightly

Joan, In the box where you are placing the switch, you should have three pairs of wires. Each pair should have a black wire and a white wire (plus each pair should have a bare ground wire). One pair of wires goes out to the bedroom entry. Another pair goes out to the closet light. The third pair should be coming from your electric panel and provides the power - this is the hot pair. First determine which pair is the hot pair. If you don't have a meter or tester, you can temporarily connect each pair in turn to a lamp and turn on the power. Repeat until you find the pair coming from the panel. Turn off the power. Now take note of the four screws on the switch. Two of the screws on one side may have a small metal bar connecting the two screws together. With the power off, connect the black hot wire to one of these two screws. If there is no metal bar you will have to use a short jumper wire between two screws on one side of the switch to connect them together. Connect one other black wire to either screw on the other side of the switch. Connect the last black wire to the last screw. (There is also probably a green screw by itself. Connect one of the ground wires to this, and wrap the other two ground wires tightly around the ground wire you connected to the green screw.) Now connect all three white wires together (not to the switch) with a wire nut. Install the switch in the box and turn on the power. Please vote if you found this helpful. Good luck, and be safe, Al K

I would suggest this generic Power On switch,

1) http://www.directron.com/atxswitch.html,

and the Red, and Black twisted pair of wires go to the Power On switch.

Your statement of ,"....don't know which of the colored pairs of wires go.....", leads me to believe you may have all of the Front Panel wires disconnected.

How about information as to where ALL the Front Panel wires go?
(Provided I have correctly interpreted your statement)

Back in the time that the eMachines T2542 was made, TriGem was the motherboard manufacturer.

The Model Name of the motherboard is Imperial, and the Model Number of the motherboard, could have been one of four variations offered.

Model Name: Imperial
Model numbers could be G, GL, GV, or GLVE
(Imperial G, Imperial GL, Imperial GV, or Imperial GLVE)

ALL four variations used the same Front Panel header.
(The connector on the motherboard the Front Panel wires connect to, is named the Front Panel header)

I would like you to view this page,

http://www.e4allupgraders.info/dir1/ecase/support/front_panel_header_support.shtml

Scroll down to the heading -
Trigem Imperial Front Panel Header Pinout.

A) Pins 1, 2, and 3 are for the Power On LED light.

B) Pins 5 and 6 are for the HarDDrive activity LED light.
(Pin 4 is not used. NC. No Connection)

C) Pins 7 and 8 are for the Power On switch

D) I wouldn't connect any wires to Pins 9 and 10, nor Pins 11 and 12

E) Pins 14 and 15 are for the Reset switch. (The button you press to restart your computer.
If the T2542 doesn't have a Reset switch, don't worry about it. There are many other ways to restart your computer)

F) Pins 17 18, and 20 are for an internal speaker.
This speaker is used for BIOS Beep Codes.

In the chart to the right, you will see GRD used many times.
GRD stands for Ground.
ANY Black wire in the twisted pair of wires, is a Ground wire.

Most of the eMachines I have worked on, use a Red, and Black pair of twisted wires for the Power On switch.
I could be mistaken on the T2542.

Best method, is to follow the color code of the wires that come from Pins 7 and 8, and be sure.

If you no longer have the manual for you're Intel D815EEA motherboard, open the link provided and download it; http://downloadcenter.intel.com/Detail_Desc.aspx?agr=Y&DwnldID=17793&ProdId=385&lang=eng
You will also need Adobe reader installed to view the manual; http://www.adobe.com/products/reader/
Read over pages 65 to 68.
Once completed turn to page 68 Figure 23. Front Panel connectors. Figure 23 shows two views.
View - (left figure), shows J9C1 as you look down at the front panel pins. The right figure will not be needed. Connect each jumper or each pair as shown.
Wire colors are important and do vary from case to case. The common color of each pair will most likely be used for negative. Wire colors such as blue, light blue, green, light green, red and light red are commonly used as positive.
Pin 1 will be positive and pin 3 will be negative. This is letter - C. Hard drive activity LED.
Pin 2 is positive and pin 4 is negative. Case power LED, and so forth.
As mentioned on page 65, the case front panel pins use 5 volts DC. If you make a mistake and place a jumper backwards (No LED light), just power off the switch on the back of the power supply and correct the jumper by turning it 180 deg. If you’re case’s LEDs do not light up than you will need to connect letter G and letter H. The electronic circuits under the motherboard should supply all 16 motherboard pins with the 5 volt DC and ground needed.

Cheers'
Mike

The power cord goes the switch terminal 1 and 3.
Terminal 2 must be the opposite of terminal 1, such that when switched on, 1 & 2 connects. Terminal 4 must be the opposite of terminal 3, such that 3 & 4 connects.
Under this setup, you may connect red to terminal 2
and black to terminal 4.
Be sure of the 1 & 2 pair, as well as the 3 & 4 pair.
then, connect the red and black wires.
Hope this will help you.

I ran into this when replacing the 3 spd switch. The replacement switch has a pair of connections at each position; you would assume the two connections are electrically tied together, they are not. The switch assembly actually has two seperate 4-position rotary switches. If your "L" wire is on the 'inner' connection, then your motor speed wires will have to be as well.

Usually the connectors will be marked as in the picture, indicating their usage. If your connectors do not have a label printed on them you can figure out the important ones. You will have a pair of connectors each for the power switch, the reset switch, the power LED and the hard drive LED. 
The two pairs of wires used for the switches are the important ones. They can be identified with a circuit tester or multimeter (Check for resistance/Ohms). When they are pressed, the meter should indicate a connection across the two wires. In the case of the power switch if it's a really old case it will toggle on and off, so watch for the continuity to change when you press it. Otherwise the reset and power switches will only register a connection when pressed, and revert to an open circuit when released. Use your multimeter to identify which pair reacts to which swtich, and label them with some masking tape and a sharpie (or equivalent way). 
As long as you identify these two and connect them correctly you'll be okay. The LEDs are not essential to booting your system and you can figure them out later. LEDs have to be connected the correct way around (usually the white wire is negative), while the switches don't matter which way they are connected as long as it's to the correct two pins. You can connect the LEDs and see which ones light up on your panel to determine which is connected where. If your power-on LED lights when there's hard drive activity, then you know that the connector plugged into the pins for HDD LED is the wires for the power LED, and so forth.

Hope this helps.
Please rate my answer.

Most likely the wires are for power, reset, and hard disk light. Touch one pair together momentarily, if your compter comes on then connect those wires to the power button. After the computer is on, connect the other two pair to the hard disk light one pair at a time until you see the light activate when the hard disk is running. Then connect the remaining pair to your reset button.

Take a peek at this link,
http://www.duxcw.com/faq/mb/frontpanel.htm

it may assist you in your problem

the +/- wires don;t really mater ! but as a general rule, the writing on the cable connectors should be facing you !

i don;t realy understand what u don;t understand, it-s easy, u guide u're self from the diagram on the motherboard (the one u tried to draw) (in the first raw on the left u put the power led cable, under it the reset cable .....)

there is no problem if u get them wrong, u can't damage anyting, so u can try until u get them right