Warning: This is an ESD sensitive process. A grounding strap MUST be worn for this process, due to the handling of circuitry. For more information, click here.

Loosen the crank on top of the applicator stand mount that is right above the printer.  Slide the whole applicator as far forward as possible. Next, move the applicator stand as close to the scale stand as possible. Turn off power to the applicator and printer using the switch on the back of the applicator (near the power cords). Remove the 2 screws at the bottom of the printer back plate.  It may be beneficial to put something on the transport to catch any screws you may drop prior to removing the screws.  Once the back cover is off, you can then locate the 4 cables and 5 screws that will have to be removed from the board, as seen to the right.
Remove the cables and screws shown above, but take care not to pull wires out of the plugs or to drop screws where they may be hard to reach. Disconnect the board from the COM cards. To do this, you will need to pull the board outward until it clears the motor, then pull the board toward you.  It may help to put a finger from the other hand between the cards, where the SATO logo is located, to assist in removing the board.
Once the board has been removed, the location where the Gap Sensor cable joins the cable coming from the board will be visible.
Disconnect the Gap Sensor cable from the board connector and go around to the side of printer where the Gap Sensor is located. The sensor is the black plastic "bar" with green tabs on top and a light purple knob on its outmost end. It is the first component through which the labels pass after entering the printer. It is held in place by 3 screws and a thin white plastic idler. Once the screws are removed, it will become possible to unsnap the sensor from the idler. Once the sensor is loose, pull it toward you.  This will free the sensor and make it possible to pull it up and remove it from the printer.
Remove the defective sensor and install the new one, following the above steps in reverse.  Once it is installed, replace the back cover to the printer.
Turn power back on to the labeler.  If the air is on, the applicator will hiss air until it finishes rebooting. Once it is again powered, make sure it is in Tamp Blow mode so it stops hissing. It will then be necessary to follow the instructions in the Gap Sensor Setup to calibrate the Gap Sensor.