Chamberlain LiftMaster Professional SW420 Installation And Maintenance Instructions

Chamberlain LiftMaster Professional SW420

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Doc 01-G0610

Rev A

Installation and Maintenance

Instructions

Swing Gate Operator

Model SW420

Table of Contents

Other manuals for Chamberlain LiftMaster Professional SW420

Owner's Manual36 pages

Questions and Answers:

M
Monique GonzalezSep 5, 2025
Why do the radio controls close my Chamberlain LiftMaster Professional SW420 from the open limit?
- W
  Whitney SanchezSep 5, 2025
  If the radio controls close the gate from the open limit on your Chamberlain Gate Opener, the radio terminals R1-4 are factory configured for residential (Open and Close) radio function. To configure terminals R1-4 for residential radio function, locate and disconnect the end of the wire running to terminal J1-1 from R4, then connect the end of the wire removed from J1-1 to J1-6.
E
Elizabeth HendersonAug 25, 2025
Why does my Chamberlain Gate Opener run, then stop and reverse direction?
- D
  Danielle WebbAug 26, 2025
  If your Chamberlain Gate Opener runs, but then stops and reverses direction, the issue could stem from several causes. The entrapment force pot might be incorrectly set; adjust it so the gate runs smoothly and reverses upon encountering an obstruction. The gate may be binding; disconnect it from the operator and manually swing it open and close to check for smooth movement. If binding occurs, repair the gate. Check red LEDs D29 and D31. The Hall Effect Sensor might be misaligned; adjust it to be within 20 thousandths of an inch of the magnets on the gearbox pulley without contact. If properly adjusted and the issue persists, replace the sensor.
A
Amy ContrerasAug 26, 2025
Why does my Chamberlain Gate Opener run slow and/or trip the internal overload?
- S
  Steven MooreAug 27, 2025
  If your Chamberlain Gate Opener runs slowly or trips the internal overload, it may be due to low primary (high voltage) power. Measure the incoming line voltage at the unit’s on/off switch and the meter base or sub panel, ensuring the voltage at the operator is within 5% of its rating when running. Check the number of amps being drawn from the panel to ensure it doesn't exceed the panel’s rating. Also, verify that the correct wire gauge was used for the distance between the breaker and operator. Inspect the motor for overheating or damage; replace it if it's humming, grinding, or making excessive noise. Note that repeated motor problems indicate poor primary power.
L
lsanchezAug 27, 2025
What to do if Master or Second Chamberlain LiftMaster Professional SW420 is not functioning properly?
- Z
  Zachary NguyenAug 27, 2025
  If the master or second operator of your Chamberlain Gate Opener is not functioning correctly, it may be due to a failure to cycle power after setup. The power to each unit must be cycled to initiate proper communication if the operators were previously in stand-alone mode. The communication wiring may be damaged or improperly wired for dual gate operation. Ensure that the communication wire is a twisted pair and is not run in the same conduit with any power wiring to avoid interference. Also, the master or second unit may not be programmed correctly, so review the program settings and check both units for proper programming.
J
James AllisonAug 28, 2025
Why does my Chamberlain LiftMaster Professional SW420 open immediately upon power up and not close?
- J
  Jessica BlackAug 28, 2025
  If your Chamberlain Gate Opener opens immediately upon power up and does not close, an accessory may be active or malfunctioning. Check the red input status LEDs, D11-D31, for any indication. If any red LEDs are on, inspect the corresponding input. The installed accessory may be incorrectly wired or malfunctioning. To troubleshoot, remove the accessory and test the operator.
S
Sonya ClarkAug 29, 2025
What to do if Chamberlain Gate Opener motor runs but gate does not move?
- K
  Kevin ValdezAug 29, 2025
  If the motor of your Chamberlain Gate Opener runs but the gate doesn't move, the belt/drive chain might be damaged or improperly tensioned. Ensure that the operator’s belt/drive chain is intact and tensioned correctly.
K
Kayla LamSep 12, 2025
What to do if my Chamberlain LiftMaster Professional SW420 master or second operator isn't working correctly?
- C
  Colton JohnsonSep 13, 2025
  If your Chamberlain Gate Opener's master or second operator isn't functioning properly, it could be due to a failure to cycle power after setup; the power to each unit must be cycled to initiate proper communication if the operators were previously in stand-alone mode. Also, the communication wiring may be damaged or improperly wired for dual gate operation; make sure that the communication wire that is used is twisted pair and not run in the same conduit with any power wiring, as this can cause interference. Finally, the master or second unit may not be programmed correctly.
B
belinda24Sep 13, 2025
Why do radio controls close the Chamberlain LiftMaster Professional SW420 Gate Opener gate from the open limit?
- H
  Heather FloresSep 14, 2025
  If the radio controls are closing the gate from the open limit on your Chamberlain gate opener, the radio terminals R1-4 are likely factory configured for residential (Open & Close) radio function. To configure terminals R1-4 for residential radio function, perform the following modifications: 1. Locate and disconnect the end of the wire running to terminal J1-1 from R4. 2. Connect the end of wire removed from J1-1 to J1-6.
W
wilsonmikeSep 4, 2025
Why doesn't my Chamberlain Gate Opener activate the timer to close after the close photo eye is broken?
- S
  Sarah MillsSep 4, 2025
  If your Chamberlain Gate Opener gate does not activate the timer to close after the close photo eye is broken, the close obstruction input is programmed incorrectly. It has been programmed to function with gate edges and not photo eyes. Reprogram the obstruction inputs to match the accessories installed on the operator.
J
John CookSep 2, 2025
How to fix Chamberlain LiftMaster Professional SW420 when programming changes do not affect the gate?
- S
  Scott BarrettSep 2, 2025
  If programming changes do not affect your Chamberlain Gate Opener, check the save switch on switch S1-1. If the switch S1-1 is in the on position, any subsequent programming changes will not affect the gate. To make programming changes, switch S1-1 off, make the desired changes, and then switch S1-1 on.

Chamberlain LiftMaster Professional SW420 Specifications

General

Motor Type	DC
Max Gate Length	16 ft
Safety Features	Obstruction Detection
Remote Control	Yes
Battery Backup	Optional

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