
The Chamberlain Group, Inc.
845 Larch Avenue
Elmhurst, Illinois 60126-1196
www.liftmaster.com
GARAGE DOOR OPENER
Model Series 1200
For Residential Use Only
Owner’s Manual
■ Please read this manual and the enclosed safety materials carefully!
■ Fasten the manual near the garage door after installation.
■ The door WILL NOT CLOSE unless the Protector System
®
is connected and
properly aligned.
■ Periodic checks of the opener are required to ensure safe operation.
■ The model number label is located on the front panel of your opener.
®
®
Model 1256R - 1/2HP
Model 1246R - 1/3HP
Model 1255R - 1/2HP
Model 1245R - 1/3HP
Model 1240R - 1/4HP

2
When you see these Safety Symbols and Signal
Words on the following pages, they will alert you to
the possibility of serious injury or death if you do
not comply with the warnings that accompany them.
The hazard may come from something mechanical
or from electric shock. Read the warnings carefully.
When you see this Signal Word on the following
pages, it will alert you to the possibility of damage to
your garage door and/or the garage door opener if
you do not comply with the cautionary statements
that accompany it. Read them carefully.
INTRODUCTION
Safety Symbol
and Signal Word Review
This garage door opener has been designed and tested to offer safe service provided it is installed, operated,
maintained and tested in strict accordance with the instructions and warnings contained in this manual.
Mechanical
Electrical
Introduction 2-7
Safety symbol and signal word review........................2
Preparing your garage door ........................................3
Tools needed...............................................................3
Planning ..................................................................4-5
Carton inventory ..........................................................6
Hardware inventory .....................................................7
Assembly 8-11
Fasten the rail to the motor unit ..............................8, 9
Install the chain and the sprocket cover .....................8
Install the chain spreader and the chain ...................10
Tighten the chain.......................................................11
Installation 11-27
Installation safety instructions....................................11
Determine the header bracket location................12-13
Install the header bracket..........................................14
Attach the rail to the header bracket.........................15
Position the opener ...................................................16
Hang the opener .......................................................17
Install the door control...............................................18
Install the light and lens ............................................19
Attach the emergency release rope and handle .......19
Electrical requirements..............................................20
Install the Protector System®................................21-23
Fasten the door bracket .......................................24-25
Connect the door arm to the trolley .....................26-27
Adjustment 28-30
Adjust the travel limits ...............................................28
Adjust the force .........................................................29
Test the safety reversal system.................................30
Test the Protector System®........................................30
Operation 31-34
Operation safety instructions.....................................31
Using your garage door opener ................................31
Using the wall-mounted door control ........................32
To open the door manually........................................32
Care of your garage door opener..............................33
Having a problem? ....................................................34
Programming 35-36
To add or reprogram a hand-held remote control .....35
To erase all codes .....................................................35
3-Button remotes.......................................................35
To add, reprogram or change
a Keyless Entry PIN ..................................................36
Repair Parts 37-38
Rail assembly parts...................................................37
Installation parts ........................................................37
Motor unit assembly parts .........................................38
Accessories 39
Repair Parts and Service 40
Warranty 40
TABLE OF CONTENTS
WARNING
WARNING
CAUTION

3
To prevent damage to garage door and opener:
• ALWAYS disable locks BEFORE installing and operating
the opener.
• ONLY operate garage door opener at 120V, 60 Hz to
avoid malfunction and damage.
To prevent possible SERIOUS INJURY OR DEATH:
• ALWAYS call a trained door systems technician if
garage door binds, sticks, or is out of balance. An
unbalanced garage door may not reverse when
required.
• NEVER try to loosen, move or adjust garage door, door
springs, cables, pulleys, brackets or their hardware, all
of which are under EXTREME tension.
• Disable ALL locks and remove ALL ropes connected to
garage door BEFORE installing and operating garage
door opener to avoid entanglement.
Preparing your garage door
Before you begin:
• Disable locks.
• Remove any ropes connected to garage door.
• Complete the following test to make sure your
garage door is balanced and is not sticking or
binding:
1. Lift the door about halfway as shown. Release
the door. If balanced, it should stay in place,
supported entirely by its springs.
2. Raise and lower the door to see if there is any
binding or sticking.
If your door binds, sticks, or is out of balance, call a
trained door systems technician.
Tools needed
During assembly, installation and adjustment of the
opener, instructions will call for hand tools as
illustrated below.
Sectional Door
One-Piece Door
WARNING
CAUTION
Carpenter's
Level (Optional)
Drill
2
1
Tape Measure
3/16", 5/16" and
5/32" Drill Bits
Pencil
Hack Saw
Wire Cutters
Claw Hammer
Pliers
Stepladder
1/2" and 7/16" Sockets
and Wrench
Screwdriver
Adjustable End Wrench

4
SECTIONAL DOOR INSTALLATION
Planning
Identify the type and height of your garage door.
Survey your garage area to see if any of the
conditions below apply to your installation. Additional
materials may be required. You may find it helpful to
refer back to this page and the accompanying
illustrations as you proceed with the installation of
your opener.
Depending on your requirements, there are several
installation steps which may call for materials or
hardware not included in the carton.
• Installation Step 1 – Look at the wall or ceiling
above the garage door. The header bracket must
be securely fastened to structural supports.
• Installation Step 5 – Do you have a finished ceiling
in your garage? If so, a support bracket and
additional fastening hardware may be required.
• Installation Step 10 – Depending upon garage
construction, extension brackets or wood blocks
may be needed to install sensors.
• Installation Step 10 – Alternate floor mounting of
the safety reversing sensor will require hardware
not provided.
• Do you have an access door in addition to the
garage door? If not, Model 1702 Outside Quick
Release is required. See Accessories page.
• Look at the garage door where it meets the floor.
Any gap between the floor and the bottom of the
door must not exceed 1/4" (6 mm). Otherwise, the
safety reversal system may not work properly. See
Adjustment Step 3. Floor or door should be
repaired.
SECTIONAL DOOR INSTALLATIONS
• Do you have a steel, aluminum, fiberglass or glass
panel door? If so, horizontal and vertical reinforcement is required (Installation Step 11).
• The opener should be installed above the center of
the door. If there is a torsion spring or center
bearing plate in the way of the header bracket, it
may be installed within 4 feet (1.22 m) to the left or
right of the door center. See Installation Steps 1
and 11.
• If your door is more than 7 feet (2.13 m) high, see
rail extension kits listed on Accessories page.
Horizontal and vertical reinforcement
is needed for lightweight garage doors
(fiberglass, steel, aluminum, door with
glass panels, etc.). See page 24 for details.
Header Wall
— — — — — — — —
Vertical
Centerline of
Garage Door
Slack in chain tension
is normal when
garage door is closed
Torsion
Spring
OR
Wallmounted
Door
Control
Extension
Spring
Access
Door
FINISHED CEILING
Support bracket &
fastening hardware
is required.
See page 17.
Header
Bracket
Chain Pulley
Bracket
Garage
Door
Spring
Motor unit
CLOSED POSITION
Trolley
Safety Reversing Sensor
Gap between floor
and bottom of door must
not exceed 1/4" (6 mm)
Safety
Reversing
Sensor
Header
Wall
Garage
Door
Straight
Door
Arm
Curved
Door
Arm
Door Bracket
Emergency
Release
Rope & Handle

5
Without a properly working safety reversal system,
persons (particularly small children) could be
SERIOUSLY INJURED or KILLED by a closing garage
door.
• The gap between the bottom of the garage door and
the floor MUST NOT exceed 1/4" (6 mm). Otherwise,
the safety reversal system may not work properly.
• The floor or the garage door MUST be repaired to
eliminate the gap.
Planning (Continued)
ONE-PIECE DOOR INSTALLATIONS
• Generally, a one-piece door does not require
reinforcement. If your door is lightweight, refer to
the information relating to sectional doors in
Installation Step 11.
• Depending on your door’s construction, you may
need additional mounting hardware for the door
bracket (Step 11).
ONE-PIECE DOOR WITH TRACK
ONE-PIECE DOOR WITHOUT TRACK
WARNING
Slack in chain tension
is normal when
Header
Wall
garage door is closed.
Access
Door
FINISHED CEILING
Support bracket
& fastening
hardw
See page 17.
Wall-mounted
Door Control
are is
required.
Motor Unit
Chain
Pulley Bracket
Trolley
Gap between floor
Safety Reversing
Sensor
and bottom of door must
not exceed 1/4" (6 mm)
Safety
Reversing
Sensor
Gap between floor and
bottom of door must not
exceed 1/4" (6 mm)
Safety Reversing
Sensor
Access
Door
Safety
Reversing
Sensor
Header
Wall
Garage
Door
Header
Wall
Chain
Pulley Bracket
Header
Bracket
Header
Bracket
Door
Bracket
Garage
Door
CLOSED POSITION
Chain
Curved
Door Arm
Door
Bracket
Straight
Door
Arm
Rail
Straight
Door
Arm
Trolley
Emergency
Rail
Release
Rope
& Handle
Curved
Door
Arm
Emergency Release
Rope & Handle

Carton Inventory
Your garage door opener is packaged in two cartons
which contain the motor unit and all parts illustrated
below. Note that accessories will depend on the
model purchased. If anything is missing, carefully
check the packing material. Parts may be stuck in
the foam. Hardware for assembly and installation is
shown on the next page. Save the carton and
packing material until installation and adjustment is
complete.
®
Lighted Door Control Button
w/6ABx1-1/2" screws
Models 1256R, 1255R,
1246R, & 1245R
Light Lens (1)
SECURITY✚
Single-Button Remote Control (1)
2-Conductor Bell Wire
White & White/Red
All Models except
1256R & 1246R
Sprocket Cover
Chain
Remote Control
Transmitter Visor Clip
Models 1256R & 1246R only
One-Piece
Rail
Styrofoam
Chain Spreader with
Screws and Washers
Y
L
ON
T
N
OU
M
G
IN
IL
E
C
P
U
Header Bracket
Safety Sensor
Bracket (2)
Chain
Pulley Bracket
Safety Labels
and
Literature
Trolley
Curved Door Arm Section
Straight Door
Arm Section
Door Bracket
(2) Safety Reversing Sensors
(1 Sending Eye and 1 Receiving Eye)
with 2-Conductor White & White/Black
Bell Wire attached

7
Hardware Inventory
Separate all hardware and group as shown below for the assembly and installation procedures.
Lag Screw
5/16"-9 x1-5/8" (2)
Lag Screw
5/16"-18x1-7/8" (2)
Self-Threading Screw
1/4"-14x5/8" (2)
Dry Wall
Anchors (2)
Clevis Pin
5/16"x2-3/4" (1)
Hex Bolt
5/16"-18x7/8" (4)
NOTICE
Handle
Carriage Bolts
1/4"-20x1/2" (2)
Clevis Pin
5/16"x1" (1)
Lock Washer 5/16" (4)
Nut 5/16"-18 (4)
Wing Nut
1/4"-20 (2)
Ring Fastener (3)
Staples (30)
Clevis Pin
5/16"x1-1/4" (1)
Rail Grease
Rope

8
To avoid SERIOUS damage to garage door opener,
use ONLY those bolts/fasteners mounted in the top of
the opener.
ASSEMBLY STEP 1
Fasten the Rail to the Motor Unit
MODELS 1255R 1245R, and 1240R
(For Models 1256R and 1246R see page 9)
• Remove the two washered bolts mounted in top of
motor unit.
• Position rail at an angle to opener so one hole in
rail and motor unit line up.
• Thread one of the washered bolts part way in.
Use only these bolts! Use of any other bolts will
cause serious damage to door opener.
• Align rail and styrofoam over sprocket. Cut tape
from rail, chain and styrofoam.
• REMOVE STYROFOAM.
ASSEMBLY STEP 2
Attach the Chain to the Sprocket
and Install the Sprocket Cover
MODELS 1255R 1245R, and 1240R
• Position chain over the sprocket. If necessary,
loosen the outer nut on the trolley to obtain more
chain slack.
• Insert the second washered bolt. CAUTION: Use
only the bolt previously removed from motor
unit!
• Tighten both screws securely through the rail into
the motor unit as shown.
• Install the sprocket cover: Insert the back tab in the
slot. Squeeze the cover slightly and insert the front
tab in the slot on the mounting plate.
Proceed to Assembly Step 3.
CAUTION
USE ONLY THIS
TYPE AND SIZE
BOLT
USE ONLY THIS
TYPE AND SIZE
BOLT
Washered Bolt
5/16"-18x1/2"
Rail
Hole
Washered Bolt
5/16"-18x1/2"
Styrofoam
Motor Unit
Sprocket
Front Tab Slot
Sprocket Cover
Back Tab Slot
Mounting
Plate

9
ASSEMBLY STEP 1
Fasten the Rail to the Motor Unit
MODELS 1256R and 1246R ONLY
• Remove the two washered bolts mounted in top of
motor unit.
• Align rail and styrofoam over sprocket.
• Cut tape from rail, chain and styrofoam. Remove
styrofoam and pull the chain back (away from the
mounting plate).
• Fasten the rail with the two washered bolts
previously removed. Tighten securely.
Use only these bolts! Use of any other bolts will
cause serious damage to door opener.
To avoid SERIOUS damage to garage door opener,
use ONLY those bolts/fasteners mounted in the top of
the opener.
CAUTION
Chain
Rail
USE ONLY THIS
TYPE AND SIZE
Styrofoam
Packaging
BOLT
Washered
Bolts
5/16"-18x1/2"
Washered Bolts
5/16"-18x1/2"
USE ONLY THIS
TYPE AND SIZE
BOLT
Motor
Unit
Sprocket
Mounting
Plate
Styrofoam
Packaging

10
ASSEMBLY STEP 2
Attach the Chain Spreader
and Re-install the Chain
MODELS 1256R AND 1246R ONLY
• Line up the holes in the chain spreader with the
holes in the motor unit as shown. The slot in the
chain spreader must fit over the Rail flange
(Figure 1).
• Securely fasten the chain spreader with the
hardware provided.
• Remove the trolley threaded shaft from the trolley
by loosening the inner nut and lock washer
(Figure 2).
• Guide the chain around the selected groove in the
chain spreader (to engage either the 8-tooth
sprocket or the 6-tooth sprocket) as shown
(Figure 3).
• Continue dispensing the chain forward to the
trolley (Figure 4). Reconnect the trolley to the
trolley threaded shaft. Proceed to Assembly
Step 3 for chain tightening instructions.
Figure 1
Figure 2 Figure 3
Figure 4
To avoid possible SERIOUS INJURY to fingers from
moving garage door opener:
• ALWAYS keep hand clear of sprocket while operating
opener.
• Securely attach sprocket cover BEFORE operating.
WARNING
#8x1"
USE ONLY
THIS TYPE
AND SIZE
SCREW
Hex Screw
Slot
Rail
Flange
Washers
Chain
Spreader
Chain
Spreader
Trolley
Threaded Shaft
Rail
Trolley
Outer
Nut
Inner Nut
and Washer
Chain
Spreader
Chain
Spreader
8-Tooth
Sprocket
Motor Unit
Mounting Plate
6-Tooth
Sprocket
Motor Unit
Mounting Plate
Install Chain
In This Direction
Sprocket

11
ASSEMBLY STEP 5
Tighten the Chain
ALL MODELS
• Spin the inner nut and lock washer down the
trolley threaded shaft, away from the trolley.
• To tighten the chain, turn outer nut in the direction
shown. AS YOU TURN THE NUT, KEEP THE
CHAIN FROM TWISTING.
• When the chain is approximately 1/2" (13 mm)
above the base of the rail at its midpoint, re-tighten
the inner nut to secure the adjustment.
Sprocket noise can result if chain is either too
loose or too tight.
NOTE: When installation is complete, you may
notice some chain droop with the door closed. This is
normal. If the chain returns to the position shown
when the door is open, do not re-adjust the chain.
NOTE: During future maintenance, ALWAYS pull the
emergency release handle to disconnect trolley
before adjusting chain.
You have now finished assembling your garage
door opener. Please read the following warnings
before proceeding to the installation section.
IMPORTANT INSTALLATION INSTRUCTIONS
1. READ AND FOLLOW ALL INSTALLATION WARNINGS
AND INSTRUCTIONS.
2. Install garage door opener only on properly balanced
and lubricated garage door. An improperly balanced
door may not reverse when required and could result in
SEVERE INJURY or DEATH.
3. All repairs to cables, spring assemblies and other
hardware MUST be made by a trained door systems
technician BEFORE installing opener.
4. Disable all locks and remove all ropes connected to
garage door BEFORE installing opener to avoid
entanglement.
5. Install garage door opener 7 feet (2.13 m) or more
above floor.
6. Mount emergency release handle 6 feet (1.83 m) above
floor.
7. NEVER connect garage door opener to power source
until instructed to do so.
8. NEVER wear watches, rings or loose clothing while
installing or servicing opener. They could be caught in
garage door or opener mechanisms.
9. Install wall-mounted garage door control:
• within sight of the garage door.
• out of reach of children at minimum height of 5 feet
(1.5 m).
• away from all moving parts of the door.
10. Place entrapment warning label on wall next to garage
door control.
11. Place manual release/safety reverse test label in plain
view on inside of garage door.
12. Upon completion of installation, test safety reversal
system. Door MUST reverse on contact with a
1-1/2” (3.8 cm) high object (or a 2x4 laid flat) on
the floor.
To reduce the risk of SEVERE INJURY or DEATH:
INSTALLATION
To Tighten Outer Nut
Trolley
Chain
Base of Rail
Outer Nut
Mid Length of Rail
Lock
Washer
1/2" (13 mm)
Inner Nut
To Tighten
Inner Nut
WARNING

12
INSTALLATION STEP 1
Determine the Header Bracket
Location
Installation procedures vary according to garage door
types. Follow the instructions which apply to your
door.
SECTIONAL DOOR
AND ONE-PIECE DOOR WITH TRACK
1. Close the door and mark the inside vertical
centerline of the garage door.
2. Extend the line onto the header wall above the
door.
You can fasten the header bracket within 4 feet
(1.2 m) of the left or right of the door center
only if a torsion spring or center bearing plate
is in the way; or you can attach it to the ceiling
(see page 10) when clearance is minimal. (It
may be mounted on the wall upside down if
necessary, to gain approximately 1/2" (1 cm).)
If you need to install the header bracket on a 2x4
(on wall or ceiling), use lag screws (not provided)
to securely fasten the 2x4 to structural supports as
shown here and on page 13.
3. Open your door to the highest point of travel as
shown. Draw an intersecting horizontal line on the
header wall 2" (5 cm) above the high point. This
height will provide travel clearance for the top edge
of the door.
Proceed to Step 2, page 14.
One-piece
door with
horizontal
track
To prevent possible SERIOUS INJURY or DEATH:
• Header bracket MUST be RIGIDLY fastened to
structural support on header wall or ceiling, otherwise
garage door might not reverse when required. DO NOT
install header bracket over drywall.
• Concrete anchors MUST be used if mounting header
bracket or 2x4 into masonry.
• NEVER try to loosen, move or adjust garage door,
springs, cables, pulleys, brackets, or their hardware, all
of which are under EXTREME tension.
• ALWAYS call a trained door systems technician if
garage door binds, sticks, or is out of balance. An
unbalanced garage door might not reverse when
required.
Sectional door
with curved
track
WARNING
Header
Wall
Ceiling
Finished
Ceiling
2x4
Vertical
Centerline
of Garage Door
Structural
Supports
Header Wall
2" (5 cm)
Highest Point
of Travel
Door
Door
Track
Header Wall
2" (5 cm)
Highest Point
of Travel
Track