Subaru Outback Alternator: Specs, Fitment & Common Faults

A genuinely definitive diagnostic technique: removing the alternator belt and starting the engine confirms or rules out the alternator entirely — plus a cautionary account of a reconditioned alternator causing its own persistent noise.

Illustration for editorial purposes

OEM Part Numbers

Accuracy note: we weren't able to verify a confident Subaru Outback alternator part number at the time of writing. Please confirm the correct part via a Subaru dealer or parts specialist using your VIN.

Often Blamed on the Battery Instead

A weak battery and a failing alternator produce almost identical symptoms at first — dim lights, slow starts, a car that won't hold charge — which is exactly why so many people replace the battery, only to be back at the garage a few weeks later with the real culprit untouched.

Before you buy: alternator output rating varies by engine size and trim, particularly on cars with more onboard electronics. Always confirm against your VIN before ordering.

What It Does

The alternator generates electricity while the engine runs, charging the battery and powering the car's electrical systems directly. A healthy alternator means the battery is mostly there for starting the engine and covering brief demand spikes — not for actually running the car's electronics on its own.

Fitment & Compatibility

Alternator output rating differs between engine sizes and trims of the Outback, with higher-spec cars carrying more onboard electronics that demand a higher-output unit. Always confirm the exact part number for your specific engine before ordering. Whether you're sourcing a replacement alternator for your Subaru Outback from a dealer, specialist, or online marketplace, always check compatibility against your registration or VIN before buying.

Common Faults

Symptoms of Failure

Dashboard battery warning light — the most direct signal, though it can also indicate a battery or wiring fault rather than the alternator itself.
Dimming or flickering headlights — especially noticeable at idle or low revs, when the alternator struggles most to keep up with demand.
Whining or grinding noise from the engine bay — can point to a worn bearing inside the alternator itself.
Battery repeatedly going flat — if a new battery keeps discharging, the alternator is often the real cause rather than the battery being faulty again.

DIY Replacement Difficulty

This is a moderate DIY job on most versions, though access varies significantly depending on engine layout — some require removing other components to reach the alternator, which can extend the job considerably. Expect 1–3 hours for an experienced home mechanic depending on access, or around an hour of labour at a garage with the right tools.

A Genuinely Definitive, Real Diagnostic Technique Worth Knowing

If you're chasing a whine or squeal that might be coming from the alternator, the power steering pump, or a belt tensioner, this is genuinely worth knowing: removing the alternator's drive belt entirely and briefly starting the engine to see whether the noise disappears is a genuinely definitive way to confirm or rule out the alternator itself, since with the belt removed the alternator physically cannot be spinning or making noise. If the noise persists with the belt off, the alternator is ruled out entirely and the cause lies elsewhere in the accessory belt system; if it disappears, you've confirmed the alternator or its own pulley bearing as the genuine source.

A genuinely honest, cautionary account worth knowing before fitting a reconditioned unit: one documented case saw a persistent electrical whirring noise begin immediately after fitting a refurbished alternator, with the noise persisting even after the unit was independently bench-tested as fine and then swapped for another unit from the same supplier — suggesting genuine quality control concerns can affect reconditioned alternators specifically. If a new noise begins right after fitting a reman or refurbished unit, it's worth considering the replacement part itself as a genuine possible cause, rather than assuming the noise must be coming from somewhere else on the car.

It's also genuinely worth knowing that on H6-equipped models, the alternator differs from the four-cylinder H4 versions, and some noise specifically under a genuinely heavy electrical load has been described by at least one professional rebuilder as difficult to reproduce except under loads well beyond what the car would typically draw at idle — worth bearing in mind that not every noise heard only under heavy load necessarily indicates a fault.

OEM vs. Aftermarket

Reputable aftermarket alternators are generally a safe, cost-effective alternative to OEM parts, provided they match the correct output rating for your specific trim. Remanufactured units from established brands are also a solid middle-ground option, often coming with a warranty comparable to new parts at a lower price.

More Subaru Alternator Guides

The same part, covered across other Subaru models.