[Micheline]

Hello,
I'm changing a 3 prong to a 4 prong plug and have bumped into a problem. There is already a green plug connected to the dryer and I don't know what to do with the green wire that came attached to the cord. Should I disconnect the one already there? Should I connect it along with the other? should I leave it as is and just let the extra wire just hang? I'm afraid of blowing everything up. Please help. Thank you.

[Fixit Man]

You MUST hook the green (ground) wire on your new pigtail to the ground
terminal on your dryer. This is VERY IMPORTANT! If you leave it dangling your dryer won't be grounded which is dangerous. I'm assuming the other green wire your describing is on the dryer and is on or near a ground terminal. If that's the case your pigtail ground and that one should be fastened tightly together on the same terminal. If still in doubt, ask the electrical guy at your local home improvement store.

[denman]

Same as Fixit Man just stated differently as it is very important that this is done correctly.

The following may also help
http://www.applianceaid.com/general.html#3to4

On a 3 wire hook up Neutral and earth ground are the same in the line cord/receptacle.
So there is a ground strap from the terminal strip's center connector to the machines frame.

On a 4 wire hook up Neutral and earth ground are separate in the line cord/receptacle.
So the ground strap in the machine is removed/disconnected.
The line cord Neutral (white) is connected to the terminal strips center connector.
And the line cord earth ground (green) is connected to the machine's frame.

[Fixit Man]

Thanks for clarifying denman, a picture is worth a thousand words!

[methowelectric]

The ground terminal inside of the dryer, the green screw, has a wire or strap from the center terminal (neutral). This is the 3-wire system, neutral and ground together. To change this to a 4-wire system, take the wire/strap from the green screw and place it on the center neutral terminal on the terminal block. Put the ground wire of the 4-wire cord under the green screw only. The red, black (L1 & L2) go to the terminal block on the left and right terminals, and the white wire from the 4-wire cord goes to the center terminal along with the strap/wire that was removed from the dryers green ground screw. Neutral and ground MUST be separated in a 4-wire electrical system throughout the system. jf