LiftMaster MJ Medium-Duty Logic Jackshaft Operator Replacement Parts

Liftmaster K20-5150-LD-1 Motor, 1/2HP, 120V

$294.37

(1)

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Liftmaster 17-10363 Pulley, 1-5/8" OD, 1/2" B, 4L Belt K17-10363

$21.48

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Liftmaster K75-10359 Brake Mounting Plate

$33.86

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Liftmaster 17-10336 Pulley, 7" OD, 3/4" B, 4L Belt

$22.33

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LiftMaster 10-10713M1 Right Hand Frame Replacement

$52.70

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LiftMaster 10-10714M1 Left Hand Frame Replacement

$52.70

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LiftMaster K-MJ5011 E-Box for MJ5011 Operator

$498.02

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LiftMaster K75-10722 Disconnect Plate for MJ and HMJ Operators

$96.41

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LiftMaster 11-10706 Clutch Shaft for Commercial Operators

$23.02

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LiftMaster 15-10717 Dual Sprocket 48B10/41A24

$39.09

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LiftMaster K74-31243 MOV Kit for Logic Commercial Operators

$58.71

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Liftmaster K10-33850 E-Box, Cover, MH, MJ, MT

LiftMaster K10-33850 E-Box Cover for MH, MJ and MT Commercial Operators

$73.94

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LiftMaster K72-33872-1 Limit Switch Shaft and Sprocket Kit

$74.95

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LiftMaster K72-33872-2 Limit Switch Shaft Kit for MGJ Commercial Operators

$76.18

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LiftMaster K72-12493 Limit Switch Kit for Medium-Duty Commercial Operators

$29.50

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Liftmaster K94-33961 Wire Harness Kit, MT, MJ, MH

LiftMaster K94-33961 Wire Harness Kit for MT, MJ and MH Operators

$66.37

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Liftmaster K0016424 Logic Board, Medium Duty, U, 315MHz

LiftMaster K001A6424 Logic Board, Medium Duty U, 315 MHz

$144.95

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Liftmaster K23-10041 Limit Switch Replacement Kit (SPDT, 10A 125/250VAC) 1/2 HP

LiftMaster K23-10041 SPDT 10A Limit Switch for Select 1/2 HP Commercial Door and Gate Operators

$15.25

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Liftmaster K29-10338 Motor Capacitor 70MFD 50/60Hz 230VAC MT BMT MJ MH HMJ MHS

LiftMaster K29-10338 70 MFD 230VAC Motor Capacitor for Commercial Door Operators

$39.95

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Liftmaster K22-240 Brake Solenoid (240V/60Hz) Replacement Kit Logic 5.0 Gate

LiftMaster K22-240 Brake Solenoid 240V/60Hz Replacement Kit for Logic 5.0 Operators

$79.57

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LiftMaster 16-4L290 Cogged V Belt (1/2" x 29") Replacement Part Medium-Duty

$31.60

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Liftmaster K13-10024 Limit Nut Replacement Part Commercial Door Operators

$11.73

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Liftmaster K001A6424 Logic Board Medium Duty U 315Mhz Commercial Door Operators

$144.95

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Liftmaster K13-10024 2-Pack Limit Nut Replacement Part Commercial Door Operators

$22.00

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Liftmaster K29-10338 Motor Capacitor, 70MFD, 50/60Hz, 230V

$39.95

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LiftMaster K11-10705 Commercial Operator Output Shaft

$41.03

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Liftmaster 19-48027M Chain, #48x27 With ML

LiftMaster 19-48027M #48 x 27 Chain with Master Link

$14.40

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Frequently Asked Questions : Liftmaster MJ Medium-Duty Logic Jackshaft Operator Replacement Parts

Q1: What are the most common replacement parts for the LiftMaster MJ jackshaft operator?

A1: Common replacement components for the LiftMaster MJ include Medium-Duty Logic control boards, continuous-duty motors, and limit switch assemblies. Drive sprockets, roller chains, and contactors are also frequently replaced to maintain functionality.

Q2: How can I identify the correct Medium-Duty Logic board for my LiftMaster MJ operator?

A2: To find the compatible replacement control board, locate the exact part number stamped on the existing board or refer to the operator's specification plate. The replacement board must match the specific voltage and phase of the original unit.

Q3: What is the procedure for replacing the motor on a LiftMaster MJ operator?

A3: Replacing a commercial operator motor requires handling high-voltage electrical connections and heavy mechanical alignments. For safety and operational integrity, this procedure must be completed by a licensed electrician or a local qualified professional.

Q4: Why might the limit switch assembly on a medium-duty jackshaft operator need replacement?

A4: Limit switches endure constant mechanical wear during standard commercial operations. If the door consistently over-travels or fails to stop at the designated open and close boundaries, the internal cams are likely worn and require complete replacement.

Q5: What safety devices are compatible with the LiftMaster MJ operator?

A5: The LiftMaster MJ requires continuous-monitoring safety peripherals, such as commercial photoelectric sensors or optical safety edges, to comply with UL 325 standards. Consult the manufacturer's installation manual to verify that replacement sensors communicate correctly with the logic board.

Q6: Can a damaged contactor block be repaired internally on the LiftMaster MJ?

A6: The contactor acts as a high-voltage relay transferring power to the motor and is not designed for internal repair. When the electrical contacts become pitted from high-cycle commercial use, the entire contactor block must be replaced as a single unit.

Q7: Are drive sprockets interchangeable across different LiftMaster jackshaft operators?

A7: Drive sprockets must precisely match the shaft diameter, keyway dimensions, and torque specifications of the specific LiftMaster MJ operator. Always consult the manufacturer's parts diagram to select the correct mechanical sprocket to prevent system damage.

Q8: Who is qualified to replace the internal friction clutch mechanism on the LiftMaster MJ?

A8: The internal friction clutch is a tension-loaded safety mechanism designed to protect the door hardware by allowing slippage during an obstruction. Servicing or replacing this critical component requires specialized knowledge and should only be performed by a local qualified technician.

Q9: What indicates that the main drive chain on the MJ operator needs replacing?

A9: A drive chain requires replacement if it exhibits severe rust, stiff links, or excessive metal fatigue that prevents proper tensioning. Using a compromised chain can lead to slipping, improper door operation, and potential mechanical failure.

Q10: What routine maintenance is required after installing new mechanical parts on the MJ operator?

A10: Newly installed chains, sprockets, and gear assemblies must be correctly aligned, tensioned, and lubricated according to exact factory specifications. For detailed maintenance schedules and safety testing procedures, consult the technical manual provided by the manufacturer.

LiftMaster MJ Medium-Duty Logic Jackshaft Operator Replacement Parts

Products [27]

Frequently Asked Questions : Liftmaster MJ Medium-Duty Logic Jackshaft Operator Replacement Parts

Q1: What are the most common replacement parts for the LiftMaster MJ jackshaft operator?

Q2: How can I identify the correct Medium-Duty Logic board for my LiftMaster MJ operator?

Q3: What is the procedure for replacing the motor on a LiftMaster MJ operator?

Q4: Why might the limit switch assembly on a medium-duty jackshaft operator need replacement?

Q5: What safety devices are compatible with the LiftMaster MJ operator?

Q6: Can a damaged contactor block be repaired internally on the LiftMaster MJ?

Q7: Are drive sprockets interchangeable across different LiftMaster jackshaft operators?

Q8: Who is qualified to replace the internal friction clutch mechanism on the LiftMaster MJ?

Q9: What indicates that the main drive chain on the MJ operator needs replacing?

Q10: What routine maintenance is required after installing new mechanical parts on the MJ operator?