ALTERNATOR DRIVE COUPLING, OH

Cross Reference Reference only: Please verify the product is eligible for your aircraft before adding to your cart. OEM Part Number McFarlane Part Number Comment 646655OE 646655 646655R 646655

Approval: FAA PMA Sub-Component SupersedesPartNumber: 646655OE (Manufacturer: Hartzell) SupersedesPartNumber: 646655R (Manufacturer: Hartzell)

The lead time for ordering the 635796 Alternator Drive Coupling typically ranges from 5 to 10 business days, depending on availability and shipping options. For more precise timing, please check with our team.

Signs that your alternator drive coupling may need servicing or replacement include unusual vibrations or noises during operation, difficulty in generating consistent electrical power, visible wear or damage on the coupling, and reduced alternator performance. If you notice any of these issues, it’s important to inspect and address them promptly.

It is recommended to inspect the alternator drive coupling during routine maintenance checks or every 100-150 flight hours. Regular inspections help identify signs of wear or damage early, ensuring timely servicing or replacement and maintaining optimal performance. For more information on when to overhaul your drive coupling, read this blog by the AOPA.

While minor inspections and cleaning can be performed by knowledgeable individuals, it is advisable to have servicing or replacement of the alternator drive coupling done by a certified technician. They have the expertise and tools to ensure the coupling is properly serviced or replaced according to industry standards and manufacturer specifications. However, QAA does provide Alternator Coupling Tool Kits to support inspection and installation of select models.

Our overhaul service for the alternator drive coupling includes a thorough inspection for wear or damage, cleaning to remove contaminants, replacement of any worn or defective parts, and rigorous testing to ensure the coupling meets performance and safety standards. The service is designed to restore the coupling to optimal condition, extending its lifespan and reliability.

To troubleshoot issues with your alternator drive coupling, start by checking for any unusual vibrations or noises and inspecting the coupling for visible signs of wear or damage. Ensure that all connections are secure and properly aligned. If problems persist, consult the aircraft’s maintenance manual for specific diagnostic procedures or seek assistance from a certified technician to conduct a detailed inspection and identify the root cause.

Tighten the coupling nut to 300–450 in-lbs. If cotter pin slots don’t align, you may tighten further – but never exceed 450 in-lbs. Do not loosen the nut to align the slots, as this can compromise torque integrity. New or overhauled couplings must resist at least 180 in-lbs of slippage torque. Couplings in service should not drop below 140 in-lbs. Always test before installation.

Install the thrust washer with the copper-colored side facing the alternator. Incorrect installation can lead to premature failure or improper seating. Ensure you have discarded any temporary shipping spacers or washers before installation. Leaving them in place can result in gear misalignment and internal engine damage.

Whenever the alternator is removed, inspect the coupling for signs of cracking, delamination, or wear in the elastomer section. If you spot any of these signs, it may be time for a replacement.

Ensure the alternator slips into place without binding. The mounting flange should seat flush- never force the alternator into position, as this can damage internal gear components.

Always refer to Continental Service Bulletin SB11-3 and Hartzell’s Service Info Letter A-140 Rev. 1 for up-to-date procedures and compliance requirements.