3G Alternator | One-Wire, High Output, 90/130 Amp | 66-77 Ford Bronco SKU: 6013

Early Bronco High Output 3G Alternator Upgrade

Fits 1966-77 Ford Bronco with Ford 289, 302 & 351W V8 or Ford 170/200 Inline 6-cylinder

Upgrade your classic Bronco’s charging system with a High Output 3G Alternator designed to support modern electrical demands while retaining factory-style fitment. This alternator delivers strong output at idle and cruising speeds, making it a reliable solution for Broncos running EFI, electric fans, auxiliary lighting, or other added accessories.

Featuring an internally regulated, self-exciting one-wire design, this 3G alternator simplifies installation while providing consistent, dependable charging performance.

• High Output Performance: Produces approximately 90 amps at idle and up to 130 amps at speed

• One-Wire Design: Internally regulated for simplified wiring and a clean install

• Factory Bracket Fitment: Designed to bolt into factory V8 alternator brackets

• Pulley Options: Available with V-belt or serpentine pulley to match your engine setup

• 30-Month Warranty: Backed against manufacturer defects

Wiring & Installation Notes

For best results, we recommend using our #6025 Battery Charge Cable or a minimum 6-gauge charge wire when installing this alternator.

After installation, the factory ALT gauge will no longer function. We recommend upgrading to a voltage gauge, such as our #6026 Voltage Gauge, which fits the stock gauge cluster.

Physically mounting the alternator is straightforward. This unit installs in the factory alternator location using existing brackets. Simply remove the original alternator and bolt this one in place.

Fitment Note:
While designed around V8 applications, this alternator may also be used on 170 and 200 inline-6 Broncos when equipped with factory-style alternator brackets. Pulley alignment and charge wiring should always be verified during installation.

Upgrade your 66-77 Bronco or classic Ford with a high-output 3G alternator that delivers strong idle charging, simplified wiring, and factory bracket fitment.

Why a 3G Alternator Is the Right Upgrade for Your Early Bronco

Every 1966-77 Ford Bronco left the factory with a 1G alternator, regardless of engine choice. At the time, that charging system was adequate. Electrical loads were minimal, accessories were limited, and Broncos weren’t expected to idle with headlights, fans, and electronics running at the same time.

Decades later, the way Early Broncos are driven—and equipped—has changed. As modern accessories become common, the limitations of the factory charging system become increasingly hard to ignore. That’s why the 3G alternator upgrade has become a common and well-proven solution.

Understanding the Factory 1G Alternator

The original 1G alternator typically produced 38–55 amps and relied on an external voltage regulator. While reliable in its day, it offered very limited output at idle and little reserve capacity.

In modern use, that often leads to:

• Dimming headlights at idle

• Incomplete battery charging during short trips

• Voltage drop with accessories running

• Electrical issues blamed on wiring rather than system capacity

These symptoms appear on both V8 and inline-6 Broncos, though they tend to surface sooner on trucks with additional accessories or lower idle speeds.

How the 3G Alternator Solves Those Problems

The 3G alternator represents a significant step forward in charging system design while remaining simple and dependable.

Strong Idle Charging

One of the biggest improvements over the 1G is idle performance. A 3G alternator maintains stable voltage at low RPM, which is critical in traffic, on the trail, or during extended idling.

Internal Regulation

By eliminating the external voltage regulator, the 3G reduces wiring complexity and removes a common failure point. Fewer components mean improved long-term reliability.

Designed for Modern Electrical Loads

Electric fans, EFI systems, auxiliary lighting, upgraded ignition components, and onboard accessories all demand consistent voltage. The 3G alternator provides the headroom needed to support these systems without overworking the charging system.

Fitment Considerations on Early Broncos

Most V8-powered Early Broncos can run a 3G alternator using factory-style alternator brackets, maintaining proper belt alignment and a clean mounting position. This makes the upgrade predictable and straightforward for most builds.

Inline-6 Broncos share the same basic charging system architecture, and the alternator itself functions the same regardless of engine configuration. As with any high-output alternator upgrade, attention should always be paid to pulley alignment, belt length, and charge wiring.

A Practical Upgrade That Improves Reliability

The goal of a 3G alternator upgrade isn’t excess capacity—it’s consistency. By allowing the charging system to operate comfortably instead of constantly at its limit, owners typically see:

• Brighter, more stable lighting

• Improved battery life

• Fewer voltage-related electrical issues

It’s an upgrade that doesn’t change how the Bronco feels to drive—but removes a common source of frustration.

The factory 1G alternator served Early Broncos well in their original era, but modern driving and electrical demands have outgrown its design. A 3G alternator upgrade brings the charging system in line with how classic Broncos are actually used today, without sacrificing fitment or simplicity.

For most Early Broncos, especially V8-powered builds, it’s one of the most practical and confidence-inspiring upgrades you can make.