Chamberlain 3255-2M 1/2 HP Manual De Usuario

21

Follow instructions which apply to your door type as 

illustrated below and on the following page.

SECTIONAL DOORS ONLY
 Make sure garage door is fully closed. Pull the emergency 

release handle to disconnect the outer trolley from the 

inner trolley. Slide the outer trolley back (away from the 

door) about 2" (5 cm) as shown in Figures 1, 2 and 3.
Figure 1:
•  Fasten straight door arm section to outer trolley with the 

5/16"x1" clevis pin. Secure the connection with a ring 

fastener.

•  Fasten curved section to the door bracket in the same 

way, using the 5/16"x1-1/4" clevis pin.

Figure 2:
•  Bring arm sections together. Find two pairs of holes that 

line up and join sections. Select holes as far apart as 

possible to increase door arm rigidity.

Figure 3, Hole alignment alternative:
•  If holes in curved arm are above holes in straight arm, 

disconnect straight arm. Cut about 6" (15 cm) from the 

solid end. Reconnect to trolley with cut end down as 

shown.

•  Bring arm sections together.
•  Find two pairs of holes that line up and join with bolts, 

lock washers and nuts.

 Pull the emergency release handle toward the opener at a 

45° angle so that the trolley release arm is horizontal. 

Proceed to Adjustment Step 1, page 23. Trolley will

re-engage automatically when opener is operated.

Ring 
Fastener

Door
Bracket

Clevis Pin
5/16"x1-1/4"

Curved
Door Arm

Straight
Door Arm

Clevis Pin
5/16"x1"

Inner Trolley 

Outer Trolley 

Emergency
Release
Handle

Lock 
Washers 
5/16"

Nuts
5/16"-18

Door Bracket

Bolts
5/16"-18x7/8"

Lock 
Washers 
5/16"

Nuts
5/16"-18

Bolts
5/16"-18x7/8"

Cut This End

Lock Washer 5/16"

Nut 5/16"-18

Ring Fastener

Hex Bolt
5/16"-18x7/8"

Clevis Pin
5/16"x1" (Trolley)

Clevis Pin
5/16"x1-1/4" (Door Bracket)

Straight 
Door Arm

Curved 
Door 
Arm

(Groove 
facing out)

Straight 
Door Arm

Curved 
Door 
Arm