Parts for your 2015 Subaru Impreza-Alternator

2015 Subaru Impreza alternator — what it does, when to replace it, and how to look after it

Based on Subaru factory service information for the 2012–2016 Impreza with the FB20 engine, plus the owner’s manual and OE parts catalogues, the 2015 Subaru Impreza is fitted with an engine-driven alternator (smart charging type). It’s a core part of the charging system and absolutely relevant to this model.

On a 2015 Impreza, the alternator keeps the 12V battery topped up and powers the car’s electrical gear while the engine’s running — headlights, blower fan, heated seats, wipers, the lot. Subaru uses an ECU-controlled (smart) alternator that varies output to suit load and driving conditions, which helps fuel economy. So, voltage can move around more than old-school units, and that’s normal.

As part of routine servicing, it pays to give the alternator and its drive belt a once-over. A healthy unit will typically keep system voltage around 13.5–14.8 V under load, though it may dip into the low 12s during decel or light load with smart charging. If the battery light flickers, lights dim at idle, or there’s a whining/grinding noise from the front of the engine, it’s time for testing.

• Check the drive belt for cracks, glazing, or slack, and listen for pulley noise.
• Test battery health