Chamberlain 3255-2M 1/2 HP, 3245M 1/3 HP Assembly Step, Attach the Rail to the Motor Unit

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ASSEMBLY STEP 1

Attach the Rail to the Motor Unit

To avoid installation difficulties, do not run the garage door opener until instructed to do so.

To avoid SERIOUS damage to garage door opener, use ONLY those bolts/fasteners mounted in the top of the opener.

•Remove the two washered bolts mounted in top of motor unit.

•Position rail at a 45˚ 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.

USE ONLY THIS TYPE AND SIZE BOLT

Washered Bolt 5/16"-18x1/2"

Styrofoam

•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

• 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 bolts securely through the rail into the

Rail

Hole

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.

Washered Bolts

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.

5/16"-18x1/2"

USE ONLY THIS

TYPE AND SIZE

BOLT

Sprocket

Sprocket Cover

Back Tab Slot

Front Tab Slot	Mounting
	Plate

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Contents Garage Door Opener For Residential Use OnlyTable of Contents Introduction Sectional Door Preparing your garage door Tools needed One-Piece DoorONE-PIECE Door Without Track Sectional Door InstallationPlanning ONE-PIECE Door with TrackInstallation Hardware Carton InventoryAssembly Step Attach the Rail to the Motor UnitBolt previously removed from motor unit Installation Tighten the ChainInstallation Step Determine the Header Bracket LocationInstall the Header Bracket Wall Header Bracket InstallationCeiling Header Bracket Installation Attach the Rail to the Header Bracket Position the Opener Sectional Door or ONE-PIECE Door with TrackHang the Opener Install the Door Control Standard installation only Run bell wire up wallInstall the Light Attach the Emergency Release Rope and HandleElectrical Requirements Install The Protector System Important Information about Safety Reversing SensorFacing the door from inside the garage Wall installation Installing the BracketsGarage door track installation preferred Floor installation FigureMounting and Wiring the Safety Reversing Sensors Troubleshooting the Safety ReversingAligning the Safety Reversing Sensors Sectional Doors Metal, insulated or light weight factory reinforced doorsFasten the Door Bracket Wood DoorsONE-PIECE Doors Connect Door Arm to Trolley Sectional Doors onlyAssemble the door arm, Figure Adjustment procedures, FigureALL ONE-PIECE Doors Connect the door arm to the trolleyIf door does not open at least 5 feet 1.5 m Adjustment StepAdjust the UP and Down Travel Limits If the door does not close completelyTest the Down close force Adjust the ForceHOW and When to Adjust the Forces Test the UP open forceImportant Safety Check Test the Safety Reversal SystemAdjust Test The Protector SystemUsing Your Garage Door Opener OperationActivate your opener with any of the following Light feature Lock featureMULTI-FUNCTION Door Control Twice a Year Care of Your OpenerOnce a Month Once a YearHaving a PROBLEM? Symptom LED is not lit on door control Safety reversing sensors wire open broken or disconnectedDoor control or wire shorted Symptom Motor unit doesn’t operateProgramming To Add or Reprogram a Hand-held Remote ControlUsing the Learn Button Using the Door Control To Erase All Codes From Motor Unit MemoryTo Add, Reprogram or Change a Keyless Entry PIN To change an existing, known PINTo set a temporary PIN Repair Parts Rail Assembly PartsInstallation Parts Motor Unit Assembly Parts Complete with Spring washerComplete with Logic board Accessories Liftmaster Service is On Call