How do you rewire a 240V 3-wire air compressor to the newer 4-wire power cords?

Answer 1

The four wire configuration has two 120V legs and a neutral and then a common ground.

you will need to get a multimeter, set it to the "over 200 volts AC setting" then place your leads into the holes in the plug while the generator is running. this will let you find the two hot legs together they will equal 200Vac. to find the common ground power down the generator! set your meter to OHMS... make sure there is no power on when you use ohms! now take one lead and touch any exposed bare metal on the generator and the other lead into the plug until you read Zero ohms this is your common ground. the other will be neutral...

if you take the plug apart, the two hot will be either red or black or both the neutral will be white and the common ground green. this is the quickest way to tell the legs

now that you have identified the legs find a plug that works for your amp draw talk to a hardware store electrician for help on the plug...

and hook it up

p.s. The 220V appliance you are hooking up doesnt use the neutral (white) wire

Answer 2

The "old" 3-wire cord had 2 "hot" wires and a ground. The "new" cord has 2 "hot" wires, a ground, and a neutral. If this does not help, call an Electrician....pkazsr The only advantage I see for doing this would to be able to access a four wire receptacle.Buy a four wire cord connect the red and black wires to the motor starter termianls or pressure switch, connect the green(ground) to the ground terminal. You have no need for the white wire,tape the end up and stuff it in to the terminal box.