Parts for your 2015 Subaru Forester-Drive belt tensioner

2015 Subaru Forester drive-belt tensioner

Based on factory workshop literature for the 2015 Forester and OEM parts catalogues used by dealerships in Australia and New Zealand, a drive-belt tensioner is relevant to this model. Petrol and diesel variants use a tensioning mechanism on the main accessory belt, while the A/C drive uses a stretch-fit belt without a tensioner. Subaru service information for FB/FA engines specifically notes the stretch-fit A/C belt procedure (no adjuster), and parts diagrams list an idler/adjuster or spring-loaded tensioner for the main belt depending on engine variant.

This Forester’s drive-belt tensioner keeps the main accessory belt at the right tension so the alternator (and, on some engines, the water pump) spins as it should. On many 2.5i petrols you’ll see an adjustable idler that’s set and locked in place during service. Some trims, including certain turbo or diesel variants, use a spring-loaded automatic tensioner. The A/C compressor is driven by a separate stretch-fit belt, so there’s no tensioner on that circuit.

Purpose-wise, the tensioner stops belt slip and flutter, which means solid charging, stable temps and less belt squeal on cold starts. It also absorbs minor pulley misalignment and belt stretch over time. If it’s worn, the belt can glaze, fray or chirp, and you might spot a wobbly idler or hear a rattly bearing.

For servicing, a quick look each service interval goes a long way. Spin the idler by hand, listen for roughness, and check the belt for cracks or stringing. If it’s the adjustable style, a tech will set deflection/tension to spec after fitting a new belt, then recheck it after a short run-in. If it’s a spring-loaded unit, the arm should move smoothly with firm resistance and sit square when the engine’s idling. Any jumpy movement or oil contamination is a red flag.

Replacement is straightforward with the right kit. Adjustable types are reset and locked down, spring-loaded types need safe unloading and correct torque on reassembly. Many owners choose to replace the main belt and tensioner together when the belt is due or if there’s any bearing noise. Remember, the A/C stretch belt is single-use and needs the correct installation tool—no tensioner to adjust there.

• Common signs: belt squeal, flickering charge light, frayed edges, idler wobble, or chirp on start-up.
• Good practice: inspect every service, replace when noisy or during belt renewal, and confirm variant (FB/FA/EE) for the correct tensioner style.

Does the 2015 Forester actually have a belt tensioner?

Yes—on the main accessory belt. Petrol and diesel variants use either an adjustable idler or a spring-loaded tensioner. The A/C system uses a separate stretch-fit belt with no tensioner, as noted in Subaru workshop procedures for FB/FA engines.

When should the drive-belt tensioner be replaced?

There’s no fixed mileage—swap it when the bearing’s noisy, the arm’s jumpy, or the belt can’t hold tension. Many owners replace it preventatively when fitting a new main drive belt, especially if the old belt showed glazing or edge wear.

Can this be DIY’d at home?

Often, yes. An adjustable idler needs the correct set-and-lock procedure, an automatic unit needs safe spring unloading. The A/C belt is stretch-fit and requires the proper installer tool. If in doubt, it’s worth having a workshop handle it—mis-tension can shorten belt and bearing life.