Liftmaster K77-39427, COVER, GRAY, RSUL12UL
The LiftMaster K77-39427 is a gray replacement cover for select LiftMaster residential slide gate operator cabinets, most commonly tied to RSL12UL-style model references. A good operator cover protects the cabinet from rain, sunlight, insects, dirt, and tampering while keeping the operator's internal board, wiring, batteries, and mechanical service areas properly enclosed. When a cover is cracked or missing, the gate may still operate for a while, but the exposed cabinet is more likely to develop corrosion, nuisance faults, damaged battery connections, or water-related board issues. The product title in this batch uses the spelling RSUL12UL, which appears in some listings, but RSL12UL is the common LiftMaster residential slide gate model format. Confirm the installed operator data label and parts diagram before ordering or uploading final product copy.
Compatible With
Compatible with select LiftMaster RSL12UL / RSUL12UL residential slide gate operator cover applications where K77-39427 is specified. Use caution with the model spelling in older listings. Verify the operator data label, cabinet generation, and illustrated parts diagram before ordering.
Features and Specifications
| Manufacturer | LiftMaster |
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| Product Type | Gray operator cover |
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| Part Number | K77-39427 |
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| Application | Replacement cover for select RSL12UL / RSUL12UL residential slide gate operator cabinets |
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| Compatible Operator Type | Residential slide gate operators when specified by parts diagram |
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| Material / Finish | Gray outdoor operator cover |
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| Notes | Model spelling and cabinet generation should be manually verified |
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Also Known As / Related Part Numbers
K77-39427, 77-39427, LM-K77-39427. Related search/model references include RSL12UL, RSL12ULMC, RSUL12UL, and RSUL12UL Series. Related but different cover numbers include K77-39425, K77-39426, K77-39428, K77-39430, K77-37855, K77-37856, and K77-37857.
Technician Note
Use this part when the installed operator parts diagram calls for the exact LiftMaster part number. Similar covers, harnesses, bushings, and mounting plates may look close in photos but can differ by cabinet generation, model suffix, voltage/phase configuration, or mounting layout.
Before Ordering Checklist
- Confirm whether the operator label reads RSL12UL, RSL12ULMC, or another model.
- Check the parts diagram for K77-39427 before ordering.
- Compare the existing cover shape, latch, access areas, and label locations.
- Do not substitute CSL24UL, CSW24UL, or RSW12UL covers without diagram confirmation.
- Inspect batteries and control-board area if the old cover allowed water intrusion.
Important Ordering Warnings
The uploaded title contains RSUL12UL, while many references use RSL12UL. This should be manually reviewed so the website title and product compatibility do not create confusion.
Professional Advisory
Gate operator covers, harnesses, and mechanical service parts should be installed with the operator power shut off and the gate secured against movement. For high-voltage wiring, damaged conductors, exposed electrical components, or unsafe gate movement, use a qualified gate technician.
Product Questions and Answers
Is K77-39427 for RSL12UL or RSUL12UL?
The strongest product references point to RSL12UL-style residential slide gate operator applications, while some listings spell the model as RSUL12UL. Confirm the operator label and parts diagram.
Can I use this on a CSL24UL operator?
No, not unless the parts diagram specifically calls for K77-39427. CSL24UL covers commonly use other K77 cover numbers.
Does the cover include internal electronics?
No. K77-39427 is a cover component. Control boards, batteries, switches, and wiring are separate parts.
Why does model spelling matter?
LiftMaster model numbers can be similar, and a typo can point a customer to the wrong cabinet part. The operator data label and parts diagram should control the final match.
What should be inspected if the old cover was cracked?
Look for water, corrosion, insect nests, loose battery wires, damaged accessory wiring, and control-board contamination before installing the new cover.
