The LiftMaster K74-31243 is a genuine
OEM replacement Metal Oxide Varistor (MOV) kit designed to
provide critical surge protection for commercial and industrial garage door
operators. This safety component safeguards sensitive internal electronics by
absorbing excess voltage from power surges or electrical spikes, preventing
catastrophic failure of the logic board and motor control circuits.
Core Functionality
- Active
Surge Suppression: The MOV acts as an electrical
"pressure relief valve," clamping high-voltage transients to a
safe level to protect the operator's electrical system.
- Redesigned
for Efficiency: This kit includes two redesigned
MOV arrangements that are more efficient to service and are backward
compatible with older models.
- System
Integrity: Replacing a scorched or degraded
MOV is essential for restoring the built-in lightning and power-line
protection required in heavy-duty industrial environments.
Technical Specifications
- Part
Number: K74-31243 (also identified as
K76-37987, K76-38000, K76-38001, or K76-37941)
- Voltage
Rating: Optimized for 58V applications
(frequently referenced in 580V surge suppression contexts for
higher-voltage industrial operators)
- Component
Type: Metal Oxide Varistor (MOV) Kit
- Compatibility:
Designed for Logic 3.0 (L3), Logic 4.0 (L4),
and Logic 5.0 (L5) commercial operators
Compatibility
This surge protection kit is the factory-specified
replacement for a wide range of LiftMaster 1-Phase (1PH) and 3-Phase
(3PH) commercial models, including:
- J
& H Series: Industrial-Duty Jackshaft and Hoist
operators.
- HJ
Series: Hoisted Jackshaft models.
- T
& GT Series: Trolley and Heavy-Duty Trolley
operators.
- Medium-Duty
Operators: Compatible with MJ, MH, and MT
series equipped with Logic boards.
Installation Note
The K74-31243 kit is typically installed within the
operator's electrical box (E-Box). Before installation, ensure all power to the
unit is disconnected at the circuit breaker. Because MOVs are sacrificial
components—meaning they are designed to fail in order to save the rest of the
board—it is highly recommended to inspect the logic board and transformer for
damage whenever an MOV requires replacement.
