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

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

Illustration for editorial purposes

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OEM Part Number: 7G9N-10300-CC (genuine alternator — confirm via VIN) — aftermarket alternators Bosch 0 986 084 230 / Valeo 439906

Accuracy note: Covers the Ford B-Max (2012-2017) 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)	Bosch 0 986 084 230 (150 A, freewheel pulley, 6 ribs, 54 mm, reman exchange, plug PL174, excludes vacuum pump, £47.03 surcharge); Bosch 0 986 082 220 (120 A, multi-rib rigid pulley, 6 ribs, 49 mm, reman exchange, plug PL174, excludes vacuum pump, £23.51 surcharge); Valeo 439906 (150 A, freewheel pulley, 6 ribs, 55 mm, new, original-equipment pattern); Valeo 440576 (150 A, freewheel pulley, 6 ribs, 55 mm, reman exchange with deposit, £50.24 surcharge); Valeo 440575 (120 A, freewheel pulley, 6 ribs, 55 mm, reman exchange with deposit, £48.42 surcharge); Hella 8EL 015 630-121 (120 A, freewheel pulley, 6 ribs, 54 mm, new); Hella 8EL 011 713-631 (150 A, freewheel pulley, 6 ribs, 49 mm, new); Lucas LRA03470 (150 A, freewheel pulley, 6 ribs, 54 mm, reman, plug 0213, £25.12 surcharge)
Outputs & variants	Two 120 A layouts and a 150 A layout are listed. The 120 A rigid-pulley, 49 mm unit (Bosch 0 986 082 220, AS-PL A3129, Lucas LRA03009, Ridex 4G0265) is the 1.4 and 1.6 Duratec petrol fitment; the 120 A freewheel, 54 to 55 mm unit (Hella 8EL 015 630-121, Valeo 440575, Ridex 4G0866, AS-PL A3259) and the 150 A freewheel unit (Bosch 0 986 084 230, Valeo 439906 and 440576, Lucas LRA03470, AS-PL A3267S) serve the 1.0 EcoBoost petrol and 1.5 and 1.6 TDCi diesels, with 150 A for Start-Stop and higher-load cars; 156 to 165 A BV PSH units cover the top specification.
Genuine (OE) numbers quoted	TG12C145 (AS-PL A3259, 120 A); TG15C186 (AS-PL A3267S, 150 A); TG12C079 (AS-PL A3358S, 120 A); TG12C087 (AS-PL A3129, 120 A).
Fitment notes	The rigid-pulley 49 mm petrol unit and the freewheel 54 to 55 mm unit are not interchangeable even at 120 A, so check the old pulley before ordering; all units are 6-rib with the PL174 or equivalent plug. Bosch and Ridex references exclude the vacuum pump. Reman Bosch, Valeo and Lucas units carry surcharges from £23.51 to £50.24, and the new Hella 8EL 015 630-121 shows a small £6.91 charge.

Confirm the Alternator Is Actually the Problem Before Replacing It

With the engine running, a multimeter across the battery terminals should read roughly 13.8-14.5V — readings notably below this suggest the alternator isn't charging properly, while readings significantly above 14.5V point to a failing voltage regulator instead. A whining noise that gets noticeably louder when heavy electrical loads switch on (headlights, heated rear window, air con on full) is also a strong practical indicator worth checking before assuming the worst.

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 a low-mileage genuine used alternator is frequently a safer bet than the cheapest reman option.

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

Because a weak Ford B-Max battery and a dying alternator both cause dim lights, slow starts and charge that won't hold, it's an easy mistake to replace the wrong one first. That mix-up sends plenty of people back to the garage a few weeks later, the real fault still there.

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 B-Max Alternator: Watch: Replacing It

🎬 Watch: Ford Focus C Max 1.6 Tdci Hdi Alternator Replacement Fitting (sister (focus/c-max 1.6 tdci))

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Engine match only (1.6 TDCi was fitted to B-Max); no B-Max or Fiesta Mk7 alternator video found.

Ford B-Max Alternator: What It Does

Every time the Ford B-Max's engine runs, the alternator is generating the electricity that charges the battery and directly feeds the electrical systems. A properly working alternator leaves the battery mostly responsible for engine starts and short demand spikes — not for running the electronics unaided.

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Ford B-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.