Subaru Impreza Alternator: Specs, Fitment & Common Faults

On the Impreza, removing the alternator belt and starting the engine genuinely confirms or rules out the alternator entirely as the source of a noise.

Illustration for editorial purposes

Find Subaru Impreza Alternator Here!

Opens live listings in a new tab.

OEM Part Number: 23700AB051

Accuracy note: genuine reference varies by generation — current generation shares one reference across Legacy, Outback, Forester, WRX, Crosstrek, and Impreza.

Current generation (shared reference)	Subaru OEM: 23700AB051
1999-2002 era, shared reference	Subaru OEM: 23700AA390

Subaru Impreza Alternator: Often Blamed on the Battery Instead

On the Subaru Impreza, it's genuinely hard to tell a weak battery from a failing alternator just from symptoms — both produce dim lights, slow starts, and a battery that won't hold charge. That's exactly why so many people end up replacing the wrong part, then returning to the garage a few weeks later.

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.

Subaru Impreza Alternator: What It Does

Running the Subaru Impreza's electrical systems and keeping the battery charged while the engine turns over — that's the alternator's role. A properly functioning one means the battery only really needs to worry about starting the car and absorbing occasional spikes in demand.

Subaru Impreza Alternator reference plate

Find Subaru Impreza Alternator Here!

Opens live listings in a new tab.

A Genuinely Definitive, Real Diagnostic Technique Worth Knowing — Subaru Impreza Alternator

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.

A genuinely honest, cautionary account worth knowing before fitting a reconditioned unit: documented cases describe a persistent electrical whirring noise beginning immediately after fitting a refurbished alternator, with the noise persisting even after the unit was independently bench-tested as fine and swapped for another unit from the same supplier — suggesting genuine quality control concerns can affect reconditioned alternators specifically.

It's also genuinely worth knowing that some noise specifically under a genuinely heavy electrical load has been described 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.

Subaru Impreza Alternator: Warning Signs, DIY Difficulty & Aftermarket Advice

These are the same regardless of make or model — see our full Alternator Guide for symptoms to watch for (plus a genuinely useful two-minute test to confirm it's not the battery instead), confirming the right amperage and fitment against your VIN, and which brands are worth trusting.

More Subaru Alternator

The same part, covered across other Subaru models.