Remove the screw which secures the limit switch cover and lift the cover
(7) Ensure that the limit switch cover is off, then slide the gear motor
forward and lift up to disengage the chain from the sprocket.
(8) Ensure that the chain is disengaged from the sprocket and lift up on the
lift assembly to its full extended up position (a helper will be required).
(9) Remove the faulty motor by removing the junction box cover and
disconnecting the three motor wires inside the box and removing the motor lead from
(10) Install the new motor as explained in procedure a. above, steps (9)-(22).
(11) Replace the chair mount casting back into place and assemble the
upper guide to the chair mount casting in the same manner that it was removed. Be
careful not to get the four adjustment nuts and the sleeves mixed up or change the
(12) Test using the procedures explained in a. above, steps (23)-(25).
REPLACING THE BACK MOTOR ASSEMBLY
The dental chair back continues to move after motor has stopped running. You
have isolated the malfunction to insufficient friction in the back motor and the screw
tube. You must replace the back motor assembly.
a. Raise the chair to its maximum height with the back to the full upright and the
seat to the full uptilt.
b. Disconnect the power.
c. Detach the back skirt from the bellows cover.
d. Remove and retain the four #10 screws that secure the bellows cover to the
bellows hangers and lower the bellows.
When you remove the pivot pins in the next step, e., the section will
drop. Support the chair toe when you are removing the pivot pins.
e. Loosen the set screws on the seat motor screw tube pivot pins. Support the
toe section of the chair and pry the pivot pins out of the pivot castings.
f. Raise the toe section of the chair and place a wood block between the pivot
casting and the chair mount casting. See figure 3-7.