Limit Switch Adjustment - Chamberlain LiftMaster Professional SW420 Manual

WARNING
CAUTION
NEVER place hands or tools inside operator or near drive
mechanism unless power is off.
NOTE: For limit location and configuration refer to Figure 1
1. Before turning on power, disconnect extension arm from gate bracket
so gate is no longer connected to operator. Push manual release pin
up through the control arm, slide clevis pin in place and secure with
a cotter pin.
2. The (3) collars are held to shaft by set screws. The collars should
now be loose on the shaft. If not, loosen all set screws until collars
are moving freely on shaft.
TO ADJUST CLOSE LIMIT SWITCH
3. Turn on electrical power.
WARNING
CAUTION
When following limit switch adjustment procedure, the motor
belt will turn and the control arm will move during some
steps. Keep hands and tools out of operator and away from
arm and drive shaft unless power is off or serious injury may
occur.
WARNING
CAUTION
Be aware that operator arm may start to move if a control
device has been improperly connected. Keep hands and tools
out of operator and away from arm and drive shaft.
4. Press CLOSE button (if installed) or connect terminals 4 & 5 on J1
terminal strip to cause the gate to close. The control arm should
move in the close direction.
5. When control arm is pointed in approximate direction of gate bracket
(on fully closed gate) press STOP button or release terminals to stop
control arm.
NOTE: If control arm does not move far enough to point in proper
direction, the close limit switch has been prematurely actuated. Turn off
power, loosen set screw on close limit cam and rotate nut away from
close limit switch. Repeat steps 3 & 4 until control arm is pointed in
correct direction.
L I M I T S W I T C H A D J U S T M E N T
6. Turn off power. Be sure close limit cam is freely turning. Rotate cam
in close direction. Stop when cam just clicks close limit switch.
Tighten set screw.
7. Reconnect gate bracket to extension arm. If arm has moved too far in
close direction to allow connection of gate bracket turn off power,
connect terminals 5 & 7 to rotate arm in opposite direction, and press
STOP button when arm is in desired position.
TO ADJUST OPEN LIMIT SWITCH
8. Turn on power. Press OPEN button (if installed) or connect terminals
5 & 7 on J1 terminal strip. Gate should open. If gate does not open
the open limit cam may be already actuating open limit switch or an
improper electrical connection may have been made. Turn off power,
inspect, correct and repeat this step.
9. When gate reaches desired fully open position press STOP button or
release terminals. Turn off power. Limit cam should turn freely.
Rotate cam in open direction. Stop when cam just clicks the open
limit switch. Tighten set screw.
10. Fine tune both switch settings by using J1 terminals 4 & 5 (to
CLOSE) of 5 & 7 (to OPEN) and the factory supplied STOP button
to move gate and rotating limit collars slightly to alter gate travel.
Rotate cam away from limit switch to increase travel, toward switch
to decrease travel.
Auxiliary
Open Limit
Cam & Collar
Limit A
Cam & Collar
Limit B
Cam & Collar
LIMIT DIRECTION
DIRECTION OF
GATE TO OPEN
RIGHT
LEFT
17
WARNING
WARNING
WARNING
WARNING
WARNING
Limit Switch A
Limit Switch B
WARNING
Figure 1
OPEN CLOSE
LIMIT LIMIT
A B
B A