Liftmaster K74-50278, E-BOX ASSEMBLY, Q403
The LiftMaster K74-50278 is the Q403 electronic e-box assembly used in select LiftMaster / Elite commercial gate operator systems. The e-box is the area that supports and protects important electrical and control components inside the operator. In service work, this kit may be needed when the original enclosure is physically damaged, badly corroded, modified, or no longer provides proper mounting support for control accessories.
This is not a universal control-board upgrade kit. Fitment depends on the operator family, enclosure style, internal component layout, and whether the machine uses the older Elite / Omni style control system. Some listings connect this part to Elite SL3000 and CSW200 applications, with Q403 and Q402 appearing as related references. Before ordering, compare the existing e-box, mounting points, control-board style, and parts diagram.
Compatible With
- Select LiftMaster / Elite SL3000 commercial slide gate operators where the parts diagram calls for K74-50278 / Q403
- Select LiftMaster / Elite CSW200 commercial swing gate operators where the parts diagram calls for K74-50278 / Q403
- Older Elite / Omni-control style gate operator electrical enclosure applications
- Not a direct substitute for switch channel Q408, maglock adapter Q400, surge protector Q310/Q410, or a main control board
Features and Specifications
| Manufacturer | LiftMaster |
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| Product Type | Electronic e-box assembly |
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| Part Number | K74-50278 |
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| Application | Replacement electrical box assembly for select commercial gate operators |
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| Compatible Operator Type | Select LiftMaster / Elite SL3000 and CSW200 style systems |
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| Notes | Verify enclosure style, mounting points, and internal component layout |
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Also Known As / Related Part Numbers
- K74-50278
- 74-50278
- Q403
- Elite Q403
- Q402
- Elite Q402
- Electronic box assembly
- E-box assembly
Technician Note
Match this replacement part to the original part number, operator model, and parts diagram. LiftMaster and Elite service parts often look similar across operator families, but small differences in mounting, wiring, generation, voltage, or mechanical layout can make them non-interchangeable.
Before Ordering Checklist
- Confirm the operator model and model suffix on the nameplate.
- Compare the existing part number, Q number, or old reference number when available.
- Review the operator parts diagram for the exact assembly location.
- Check for damage that may have caused the original part to fail, such as water intrusion, gate binding, worn chain, loose hardware, or incorrect wiring.
- For electrical parts, confirm voltage, control-board generation, grounding, and accessory wiring before installation.
Professional Advisory
Gate operator repairs can involve heavy moving gates, stored mechanical force, high voltage, and required entrapment protection devices. Do not bypass safety sensors, edge devices, interlocks, or emergency release requirements. When wiring, grounding, high-voltage diagnosis, or unsafe gate movement is involved, have the system serviced by a qualified gate technician.
Product Questions and Answers
Is K74-50278 the same as an Omni control board?
No. K74-50278 is an electronic box assembly. The control board, surge board, relay adapters, and wiring components are separate unless specifically included by the kit.
What models commonly use this e-box assembly?
References commonly associate it with select Elite SL3000 and CSW200 commercial gate operators, depending on generation and parts diagram.
Why is Q402 listed with Q403?
Some sources list Q402 as a related reference. Treat it as a related or search number unless the parts diagram confirms it as the correct replacement for your operator.
When would this part be replaced?
It may be replaced when the original electrical box is damaged, corroded, modified, or unable to properly support the control components.
Does installation involve high voltage?
It can. E-box replacement may involve line voltage, grounding, and control wiring. A qualified gate technician should perform the work if wiring is involved.
