Ford S-Max Alternator: Specs, Fitment & Common Faults

A simple multimeter test confirms whether it's genuinely the alternator — and why some replacement units develop the same fault.

Illustration for editorial purposes

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OEM Part Number: AG9T-10300-BA (genuine alternator — confirm via VIN) — aftermarket alternators Valeo 440713 / Hella 8EL 015 630-791

Accuracy note: Covers the Ford S-Max (2015-) as listed in the UK aftermarket catalogues. Alternators are sold by output (amps), pulley type and plug, and the same model usually has two or three units depending on engine, start-stop and the electrical load of the trim — a 120 A unit on a car built for 150 A will undercharge, and a rigid pulley on a car designed for a freewheel clutch pulley will shred belts. The references below are UK aftermarket catalogue listings for this generation, labelled by brand; many are remanufactured exchange units that carry a core charge until the old alternator is returned. Genuine numbers are shown only where a listing quotes one. Check the amp rating, pulley and plug stamped on the old unit, or confirm via VIN, before ordering.

Alternators (aftermarket)	Valeo 440713 (180 A, freewheel clutch pulley, 6 ribs, 56 mm, reman premium exchange, B+, four-point mounting, L39 position, core charge GBP 50.24); Valeo 440780 (250 A, freewheel clutch pulley, 6 ribs, 56 mm, reman premium exchange, M8, L37 position, core charge GBP 50.24); Hella 8EL 015 630-791 (220 A, V-ribbed pulley, 6 ribs, 55 mm, new, qualified fitting advised); AS-PL A3524S (220 A, freewheel clutch pulley, 6 ribs, 54 mm, new, PL_2305 plug); AS-PL A3512S (225 A, freewheel clutch pulley, 6 ribs, 54 mm, new, PL_3402 plug); AS-PL A3569S (235 A, freewheel clutch pulley, 6 ribs, 54 mm, new, PL_3402 plug); Ridex 4G1292 (180 A, freewheel clutch pulley, 6 ribs, 54.2 mm, new, integrated regulator, excludes vacuum pump); Ridex 4G1413 (230 A, freewheel clutch pulley, 6 ribs, 54 mm, new, excludes vacuum pump).
Outputs & variants	As on the Galaxy and Mondeo, outputs are 180 A, 220 A, 225 A, 230 A, 235 A, 240 A and 250 A on 54 to 56 mm six-rib freewheel clutch pulleys. The 180 A units are the base diesel fitment, 220 to 235 A serve the higher-spec 2.0 TDCi and EcoBlue diesels and 1.5/2.0 EcoBoost petrols, and the 250 A Valeo is the top output. One 230 A BV PSH unit uses a four-rib 60 mm pulley and is the exception.
Genuine (OE) numbers quoted	AS-PL A3524 quotes Valeo 439994; AS-PL A3524S quotes FGN20S052; AS-PL A3512S quotes FG23S072; AS-PL A3569S quotes CG25S032.
Fitment notes	Confirm the amperage from the old unit because the different outputs share mountings and appearance; renew the freewheel clutch pulley with the alternator; Valeo and Ridex exchange units carry a refundable core charge of GBP 50.24 and GBP 30.14; the Ridex units exclude engines with an alternator-driven vacuum pump.

Confirm the Alternator Is the Actual Problem First

With the engine running, a multimeter across the battery terminals should read roughly 13.8-14.5V — notably lower readings suggest the alternator isn't charging properly, while readings well above 14.5V point to a failing voltage regulator instead. A whining noise that gets louder when heavy electrical loads switch on is a strong practical indicator worth checking first.

Worth knowing when buying a replacement: Several Ford owners report remanufactured or budget aftermarket alternators developing the same whining noise shortly after fitting. A well-reviewed reconditioned unit or low-mileage genuine used alternator is frequently the safer choice over the cheapest reman option.

Ford S-Max Alternator: Often Blamed on the Battery Instead

On the Ford S-Max, dim lights, slow starts, a battery that won't hold charge — these symptoms point equally to a weak battery or a failing alternator, and that overlap is why so many replacements target the wrong part first, with the real problem only surfacing 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.

Ford S-Max Alternator: Watch: Replacing It

🎬 Watch: How to replace ALTERNATOR - Ford (Volvo) 2.0 TDCi (Galaxy, S-Max, Mondeo, Kuga) (older gen)

Watch on YouTube ↗

Mk2 (2006-2015) 2.0 TDCi; the Edge video above (PcXME64uauk) is the closest for the 2015-on car.

Ford S-Max Alternator: What It Does

Electricity generation while the Ford S-Max's engine is running is the alternator's job, charging the battery and directly powering the electrical systems. When it's working properly, the battery mostly just handles engine starting and short demand spikes, not day-to-day electrical load.

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Ford S-Max 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 Ford Alternator

The same part, covered across other Ford models.