Liftmaster SW420 & SW420GL Swing Gate Parts
LiftMaster SW420 & SW420GL Replacement Parts
Genuine LiftMaster replacement parts for the SW420 and SW420GL commercial swing gate operators — the 1/3 HP belt-and-chain driven swing operator with a bolt-on arm assembly. Use the exploded diagram above to find the key number for the part you need, then click any part number in the tables below to go straight to that product.
The diagram is grouped into three lettered assemblies. A is the arm assembly, D is the drive kit inside the housing, and E is the control box. The tables below follow the same grouping.
This is an older platform and much of it is discontinued. Where a part number appears without a link, LiftMaster no longer supplies it and there is no direct replacement — including both complete kits, K75-18362 (arm) and K75-18363 (drive). Individual parts within those kits are still available where shown.
The limit collar is now supplied as 75-G0089 rather than the 75-G0089X shown in the guide.
Common SW420 Repairs
| Symptom | Usual cause | Parts to check |
|---|---|---|
| Motor runs but the gate does not move | Drive belt slipping or chain worn | K16-3L320 belt, K19-41047 chain, K17-G0475 pulley |
| Gate overruns or stops short | Limit switch or limit collar | K23-2016 limit switch, 75-G0089 limit collar |
| Motor hums but will not start | Motor capacitor | K29-10338 capacitor |
| Operator dead, no board lights | Transformer, relay or control board | K21-5115 transformer, K24-24-1 relay, K001A5566 board |
| Erratic travel or missed counts | Hall effect sensor | K74-18381 hall effect sensor kit |
| Play or knocking at the arm | Bearings, bushings or clevis pin worn | K12-10715 flange bearing, K12-2727 bushing, K80-2752 pin |
| Grinding from the drive train | Gear reducer or sprockets | K32-2100 gear reducer, K15-3001 sprocket |
| No warning tone before the gate moves | Alarm kit | K74-18655 alarm kit |
Arm Assembly (A)
| Ref | Part # | Description |
|---|---|---|
| A | K75-18362 | Arm Assembly Kit |
| A1 | K07-2705 | Arm Stop |
| A2 | K07-2706 | Arm Hub |
| A3 | K10-2111 | Gate Bracket |
| A4 | K12-10715 | Flange Bearing, 1" |
| A5 | K12-2727 | Flanged Bushing, 3/8" ID x 5/8" |
| A6 | K80-2752 | Clevis Pin |
| A7 | 82-HN38-16 | Bolt, 3/8-16 x 16" |
| A8 | K82-HN38-18 | Screw, 3/8"-16 x 18 |
| A9 | 86-HP-4 | Cotter Pin, 0.312 x 1.44, 18-8SS — no longer available |
Drive Kit (D)
| Ref | Part # | Description |
|---|---|---|
| D | K75-18363 | Drive Kit — no longer available |
| D1 | 10-2702 | Reducer Bracket — no longer available |
| D2 | 10-2703 | Bearing Bracket — no longer available |
| D3 | 10-2704 | Motor Plate — no longer available |
| D4 | 10-2706 | Plate, Switch, RSW — no longer available |
| D5 | 10-2708 | Plate, Stiffener, RSW — no longer available |
| D6 | K11-2725 | Drive Shaft |
| D7 | K12-10715 | Flange Bearing, 1" |
| D8 | 12-2726 | Flange Bearing, 5/8" Bore — no longer available |
| D9 | 15-2710 | Sprocket, 40B11T, 5/8" x 3/16" — no longer available |
| D10 | K15-3001 | Sprocket, 40B32T, 1" x 1/4" |
| D11 | 17-2744 | Pulley, 1-7/16" x 1/2", 3L Belt — no longer available |
| D12 | K19-41047 | Chain, #41 x 47, No ML |
| D13 | 20-5752-33 | Motor, 1/3 HP, 115V, 1PH, CF |
| D14 | K23-2016 | Limit Switch |
| D15 | K32-2100 | Gear Reducer, 30:1 |
| D16 | 75-G0089X | Limit Collar — supplied as 75-G0089 |
| D17 | K74-18381 | Hall Effect Sensor Kit |
| D18 | K86-RP10-110 | Roll Pin, 1/4" x 1-1/2" |
| D19 | K16-3L320 | Belt, 3L320 |
| D20 | K17-G0475 | Pulley, 6" x 5/8" |
Control Box (E)
| Ref | Part # | Description |
|---|---|---|
| E1 | K10-G0553 | Control Box Cover — no longer available |
| E2 | K21-5115 | Transformer, 115/240V |
| E3 | K24-24-1 | Relay, 24V, 10A |
| E4 | K29-10338 | Motor Capacitor |
| E4 | 29-5033 | Capacitor, 230V — no longer available |
| E5 | 42-G0569 | Terminal Block — no longer available |
| E6 | K001A5566 | GL Control Board |
Housing and Enclosure
| Ref | Part # | Description |
|---|---|---|
| 1 | 74-18465 | Housing Assembly — no longer available |
| 2 | 10-18462 | Front Cover — no longer available |
| 3 | K10-G0326 | Switch Box Cover |
| 4 | K23-3001 | On/Off Switch, 125/277VAC, 20A |
| 5 | 28-G0518 | Conduit Box — no longer available |
| 6 | K74-18655 | Alarm Kit |
| 7 | G802754 | U Nut Bolt — no longer available |