Limit Switch Adjustments - Chamberlain LiftMaster Professional SW420 Installation And Maintenance Instructions Manual

Limit Switch Adjustments

CAUTION
Never place hands or tools inside operator or near drive
mechanism unless power is off.
1 Before turning on electrical power, disconnect the extension
arm from gate bracket so that the gate is no longer connected
to the operator.
2 Push the manual release pin up through the control arm and
slide clevis pin in place. Secure clevis pin with a cotter pin.
3 Identify the limit switches.
The limit switches are actuated when the main shaft rotates and
causes the large screw heads (cams) on the collars to depress
the switch levers.
The collars should all be loose on the shaft at this point. If they
are not, loosen all set screws until collars are free moving on
the shaft.
AUXILIARY
OPEN LIMIT
CAM & COLLAR
LIMIT A
CAM & COLLAR
LIMIT B
CAM & COLLAR
CAUTION
When following the limit switch adjustment procedure,
the motor belt will turn and the control arm will move
during some of the steps. Keep hands and tools out of
the operator and away from the arm and drive shaft
unless power is off, or serious injury may result.
4 Turn on electrical power.
CAUTION
Be aware that the operator arm may start to move if a
control device has been improperly connected. Keep
hands and tools out of the operator and away from the
arm and drive shaft.
LIMIT SWITCH A
LIMIT SWITCH B
01-G0610F15
Figure 16
Limit Switch Adjustments
See Figure 16.
The (3) collars are held fast
to the shaft by means of set
screws.
DIRECTION OF OPEN
GATE TO OPEN LIMIT
Right
Left
21
CLOSE
LIMIT
A B
B A
Doc 01-G0610
Rev A