Set The Extruders Aside; Separate The Extruder Wires Into Two Bundles; Attach The New Extruders To The Mightyboard; Turn Your Makerbot Replicator 2X Upright Again - MakerBot Replicator 2X Quick Start Manual

Add the heat sink, spacers, fan, and fan guard that you removed in step 2 to the
left extruder. Use the 2.5 mm hex wrench to thread the fan assembly bolts back
into the extruder motor.

10. Set the extruders aside

The extruders are now completely detached from your MakerBot Replicator 2X.
Set them aside and unpack the new extruders.

11. Separate the extruder wires into two bundles

Separate the wires coming from the right extruder from the wires coming from
the left extruder. You may have to unwrap the cable completely to find out
which bundle is which, but it's very important. Make sure the right and left wire
bundles are labeled before proceeding.

12. Attach the new extruders to the Mightyboard

The new extruders have two thermocouples and two main extruder cables, just
like the old ones. Plug the extruder cables into the ports from which you
removed the old cables. Make sure the right cable is being plugged into the
terminal labeled "A" and the left cable is being plugged into the terminal
labeled "B."
Next, attach the thermocouples. Make sure you're inserting the thermocouple
leads into the same terminals you removed the old ones from. The right
thermocouple leads go to the terminals labelled "A" and the left thermocouple
leads go to the terminals labeled "B." The terminals are also labeled with color
names—be sure to insert the yellow and red leads into the right places.
For terminals with buttons, press the buttons on the terminals, slide the leads
all the way in, and release the buttons. For terminals with screws, slide the
leads in and tighten the screws. Tug on the leads to make sure they're secure.
You may find that it's easier to reconnect one lead at a time.
13. Return the electronics cover to the bottom of your MakerBot
Replicator 2X
Bolt it into place with the 2.5 mm hex wrench and the four bolts you set aside
earlier.

14. Turn your MakerBot Replicator 2X upright again

Make sure the wrapped extruder cable routes through the notch at the back of
the 3D printer.