Craftsman 139.18451DM Manuel D'instructions page 11

ASSEMBLY STEP 5
Tighten the Chain
1. Spin the inner nut and lock washer down the trolley threaded
shaft, away from the trolley.
2. To tighten the chain, turn outer nut in the direction shown
(Figure 1).
3. When the chain is approximately 1/4" (6 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 too loose. 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 in
Figure 2 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.
NOTE: You may notice loosening of chain after Adjustment Step 3
(Test the Safety Reversal System). Check for proper tension and
readjust chain if necessary. Then repeat Adjustment Step 3.
You have now fi nished assembling your garage door opener.
Please read the following warnings before proceeding to the
installation section.
INSTALLATION
IMPORTANT INSTALLATION INSTRUCTIONS
To reduce the risk of SEVERE INJURY or DEATH:
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
fl oor.
6. Mount the emergency release within reach, but at least 6 feet
(1.83 m) above the fl oor and avoiding contact with vehicles
to avoid accidental release.
7. NEVER connect garage door opener to power source until
instructed to do so.
Figure 1
To Tighten Outer Nut
Figure 2
WARNING
WARNING
WARNING WARNING
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 fl at) on the fl oor.
11
Outer Lock
Nut Washer
To Tighten
Inner Nut
Chain
1/4" (6 mm)
Base of Rail
Mid length of Rail
Trolley
Threaded
Shaft
Inner Nut