LiftMaster 3850 Belt Drive Replacement Parts
LiftMaster 3850 Replacement Parts
The 3850 is a belt drive opener with battery backup, running the 20 rib 41A5434 belt. Everything for it is on this page: the motor unit, the belts, the battery, the safety sensors, the door hardware, the wall control and the remote. Each section has its own diagram, and the reference numbers are specific to the diagram directly above them.
Ordering a belt? The belt is sized to your door height, not your rail. The 3850 uses the 20 rib 41A5434 belt, stocked in factory and lower cost aftermarket versions. See the belt table below, or use the full LiftMaster belt selector if you are not sure which you need.
1. Motor Unit
First part of number below corresponds to diagram number above:
| Ref | Part # | Description |
|---|---|---|
| 01 | 041C0076 | Belt cap retainer and cog |
| 02 | 041B4245-1 | Line cord, 6 ft |
| 04 | 041A6281 | Wire harness kit |
| 05 | 041D0794 | Motor with positioning sensor |
| 07 | 041A6231 | End panel with battery door and screw |
| 08 | 041C0190 | Transformer and harness |
| 10 | K108D0079M | Light lens |
| 11 | 041C0279 | Light socket |
Parts no longer manufactured. The ref 06 receiver logic board is discontinued in both frequencies — 041DB002-2 at 315MHz and 41DB002-2-390 at 390MHz — and we do not stock a replacement. Ref 03, the 41B4375-3 terminal block, and ref 09, the 41D504-4 cover, are also discontinued. Everything else on this diagram is available. If your 3850 has a failed board, call (866) 965-5599 before ordering anything else.
2. Belts
The 3850 takes the 20 rib 41A5434 belt. Measure your door opening height, not the rail. We stock the genuine LiftMaster belt and a lower cost aftermarket belt built to the same length, rib pitch and end fittings — the aftermarket belt typically runs about a third of the factory price and installs identically.
| Door Height | Belt | Factory (OEM) | Aftermarket |
|---|---|---|---|
| 7 ft | 41A5434-11 | Factory belt | Aftermarket belt |
| 8 ft | 41A5434-13 | Factory belt | Aftermarket belt |
| 10 ft | 41A5434-14 | Factory belt | Aftermarket belt |
A belt rarely fails on its own. Check the belt pulley bracket, trolley and tensioner while the rail is apart — see all belt drive rail parts.
3. Battery Backup and Bulbs
| Ref | Part # | Description |
|---|---|---|
| — | G485LM | 12V replacement battery for the backup system |
| — | LMLED1 | Universal replacement LED bulb, vibration rated |
If the opener beeps and runs slowly on battery, or will not run at all during a power cut, it is almost always just the battery. The G485LM is the part, and it sits behind the battery door on the end panel.
4. Safety Sensors and Brackets
First part of number below corresponds to diagram number above:
Current parts — order these
| Ref | Part # | Description |
|---|---|---|
| S1–S2 | 041-0136 | Safety sensor eye kit — sending and receiving eyes, supplied as a matched pair |
| S3–S4 | 041A5281-1 | Sensor extension brackets |
| — | 041-0155-000 | Safety sensor brackets, 2021 to present |
| — | 041B0873 | Sunblocker bracket — stops sunlight false-tripping the eye |
| — | Sensor Guards | Protective guards, sensors not included |
| — | 041B4494-1 | 2 conductor bell wire, 26 ft |
Superseded part numbers
The current eyes and brackets replace every earlier version, so there is no need to match your old part number — order the current part.
| Old Part # | Order Instead | Notes |
|---|---|---|
| 41A5034 | 041-0136 | Eye kit used 1997 onward, now superseded |
| 12B484 | 041A5281-1 | Square holed mounting bracket, discontinued |
| 12B485 | 041A5281-1 | Slotted mounting bracket, discontinued |
| 041A5266-1 | 041-0155-000 | Sensor mounting bracket, no longer available |
5. Remotes, Wall Controls and Door Hardware
First part of number below corresponds to diagram number above:
| Ref | Part # | Description |
|---|---|---|
| 01–02 | 893MAX | 3 button visor remote — universal replacement for all older remotes |
| 03 | 10A20 | 3V coin battery for the remote |
| 05 | 10A14 | 12V battery — 61LM series remotes |
| 06 | 041B4494-1 | 2 conductor bell wire, 26 ft |
| 07 | 041A4353 | Header bracket, 1993 to current |
| 07 | 041A4353-1 | Header bracket, black — belt drive units |
| 08 | 041A5047 | Door bracket |
| 08 | 041A5047-1 | Door bracket, black — belt drive units |
| 09 | 041A2828 | Manual release rope and handle assembly |
| 10 | 29C128 | Remote visor clip |
| 11 | 29B137 | Remote visor clip — 700 and 800 series remotes |
| 12 | 041A4166 | Lighted pushbutton, two wire |
| 13–15 | 889LM | MyQ control panel — the replacement on 1998 and newer openers |
| 16 | 041B0035B | Curved door arm |
| 17 | 4178B0034B | Straight door arm section |
| — | 041A4202-6B | Wall control panel, two wire |
| — | 041A8094 | Door arm kit — curved and straight sections together |
| — | 041A2770-17 | Installation hardware kit — bolts, staples, grease, release cord |
| — | 041A3504 | Antenna extender kit |
| — | 041A3504-1 | Antenna extender kit with adapter |
| — | L6950 | Multi purpose spray lube, green |
| — | L6960 | Multi purpose spray lube, blue |
Remote controls
The original remotes for these openers are discontinued. The 893MAX is the universal replacement and works with all the older LiftMaster, Chamberlain and Craftsman openers. It covers 371LM, 971LM, 973LM and 893LM, and is the listed substitute for 81LM, 83LM, 63LM, 753CB, 850CB, 853CB, 953CB, 953EV and Craftsman 53680, 53859 and 53879. Browse all LiftMaster remote controls.
Wall controls — superseded part numbers
| Old Part # | Order Instead | Notes |
|---|---|---|
| 98LM | 889LM | Motion detecting control panel, discontinued |
| 398LM | 889LM | Control panel, discontinued |
| 888LM | 889LM | Control panel, discontinued |
More LiftMaster Parts
Belt drive rail and belt parts · All LiftMaster opener parts · LiftMaster remote controls