120A Alternator for BMW 3 Series, 5 Series, X5 & Z3 (OE 12317510599)

A 120A Alternator Built for a Wide Range of BMW Sixes

This is a 120A alternator built to OE number 12317510599, covering a broad range of BMW inline-six models from the late 1990s through the mid-2000s. If your BMW's battery light has come on, your battery keeps dying even after a jump, or your electronics have started acting flaky at idle, a worn alternator is one of the most common causes, and this is a direct OE-spec replacement rather than a generic universal unit.

What an Alternator Does

The alternator is what keeps your battery charged and your electrical system running once the engine is on — without it, the battery would drain within minutes of starting the car. It converts mechanical energy from the serpentine belt into electrical current, using a spinning rotor and stationary stator to generate AC power that's then rectified into the DC current your car's electronics actually use. Over time, the internal brushes wear down, the bearings get noisy, and the voltage regulator can drift out of spec, all of which gradually reduce output until the alternator can no longer keep up with demand.

Vehicle Coverage

This alternator is built for BMW's M52/M54 inline-six engines across several chassis and model years: the E46 3 Series (320i 2001-2005, 323i/323Ci 2000, 325i/325Ci/325xi 2001-2006, 328i/328Ci 2000, 330i/330Ci/330xi 2001-2006), the E39 5 Series (525i 2001-2003, 528i 1997-2000, 530i 2001-2003), the E53 X5 (3.0L, 2001-2006), and the E36/E37 Z3 (2.5L and 2.8L and 3.0L variants, 1997-2002). Some of these applications use a slightly different unit depending on whether the engine has the air duct-equipped design introduced around 2004, so it's worth cross-referencing the OE numbers below against your original alternator rather than assuming fitment from model year alone.

OE and Cross-Reference Numbers

This alternator is built to OE numbers 13882, 13774, 13970, 13734, 12317510593, 12317510597, and 12317510599, and cross-references to Bosch 0 123 515 004, Valeo SG12B029, and Denso-style aftermarket numbers 12311740629 and 2542377B. If your old unit carries any of these numbers stamped on the housing, this is a confirmed match.

Specifications

• Type: Alternator, 120A
• Voltage: 12V
• Rotation: Clockwise (CW)
• Pulley groove quantity: 6 (S6 pulley class)
• Regulator type: Internal (IR)
• Material: Aluminum housing
• Placement: Front of engine
• Condition: New

Signs Yours Might Be Failing

A failing alternator usually shows up as a dashboard battery warning light, dimming or flickering headlights and interior lights (especially noticeable at idle), a battery that won't hold a charge even though it tests fine on its own, or a whining or grinding noise from the front of the engine as the internal bearings wear. Wikipedia's alternator article covers the electromagnetic principles behind how these units generate current, if you want the deeper technical background on why a worn rotor or stator causes output to drop off gradually rather than fail all at once.

Installation Notes

Alternator replacement on these BMW inline-six engines is a moderately involved job — it typically means disconnecting the battery, removing the intake hose and airflow sensor for clearance, loosening the serpentine belt tensioner, and unbolting the old unit before the new one goes in following the same steps in reverse. Access varies by chassis, with some E46 and E39 applications requiring more clearance work than others, so it's worth having a repair guide specific to your exact model on hand before starting.

Why Getting the Right Alternator Matters

An alternator that doesn't match your engine's amperage and pulley configuration can either fail to keep the battery charged under load — running the heater, headlights, and infotainment system all at once, for instance — or put the wrong charging voltage through electronics that weren't designed for it. Matching the OE numbers above against your original unit is the surest way to get a replacement that performs the way the factory alternator did.

Ordering Information

This alternator is in stock and ships ready to install. Our Shipping Information page covers current timelines, and our Warranty and Returns pages explain the process if anything isn't right on arrival. If you're not sure this matches your specific chassis and engine combination, our Request a Part page is the fastest way to confirm before ordering.

Related Parts

This alternator sits in our alternators collection and our BMW collection. If you're also chasing a starting issue, our BMW starter motor is worth checking too, since starting and charging problems on these platforms often get diagnosed together.