WAI 21939N Alternator

Alternator for Ford Super Duty

This WAI alternator is a 100% new replacement built for charging-system performance in heavy-duty applications. It delivers 175 amps and uses an internal regulator, making it a direct-fit option for Ford Super Duty trucks that need dependable electrical output.

Key Features

• 100% new alternator, not remanufactured
• 175-amp output for higher electrical demand
• Internal regulator for integrated voltage control
• Internal fan design for compact packaging
• Serpentine pulley with 8 grooves included
• Clockwise rotation with DENSO family design

Detailed Description

WAI builds this alternator with proprietary components and manufacturing processes to support long service life and consistent performance. The unit is configured with a pulley included, clockwise rotation, and a serpentine belt drive, which helps match the original charging-system layout on compatible Ford F-250 Super Duty, Ford F-350 Super Duty, Ford F-450 Super Duty, and Ford F-550 Super Duty applications. Part number 21939N is also cross-referenced to 21939 and 104211-0490 for the same application.

The DENSO family design and 175-amp rating make this alternator a practical replacement when the vehicle’s electrical system needs stable charging output for accessories and demanding operating conditions. Part number 21939N appears in Ford Super Duty fitments from 2017-2022, including F-250 Super Duty, F-350 Super Duty, F-450 Super Duty, and F-550 Super Duty models.

What It Helps Solve

• Low charging output from a worn alternator
• Battery warning lights caused by charging-system faults
• Voltage instability under electrical load
• Starting issues related to insufficient alternator output
• Accessory performance problems from weak system charging

Installation Notes and Tips

Fits 2017-2022 Ford F-250 Super Duty, N/A. Fits 2017-2022 Ford F-350 Super Duty, N/A. Fits 2017-2022 Ford F-450 Super Duty, N/A. Fits 2017-2022 Ford F-550 Super Duty, N/A. Verify pulley style, belt type, rotation direction, and amperage rating against the original unit before installation. Confirm electrical connections and charging-system condition during replacement.

Quality Assurance

WAI states that this alternator is 100% new and manufactured with proprietary components and processes to support maximum life and performance.