BMW 5 Series Alternator: Specs, Fitment & Common Faults
A genuinely useful finding for start-stop equipped models: a struggling alternator is a documented cause of the system behaving erratically — plus a note that newer mild hybrid models with an integrated starter-generator often need more advanced diagnostic tools.
Illustration for editorial purposes
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OEM Part Number: 12318634167 (genuine alternator — confirm via VIN) — aftermarket alternators Valeo 439709 / Denso DAN1126
| Alternators (aftermarket) | Valeo 439709 (180 A, freewheel pulley, 6 ribs, 55 mm, new); Valeo 444724 (180 A, freewheel, 6 ribs, 55 mm, remanufactured exchange, core charge £50.24); Hella 8EL 011 713-081 (220 A, freewheel, 7 ribs, 54 mm, new); Hella 8EL 015 630-491 (150 A, V-ribbed pulley, 6 ribs, 48 mm, new); Denso DAN1126 (170 A, freewheel, 6 ribs, 49 mm, new); Denso DAN1464 (180 A, multi-rib pulley, 6 ribs, 48 mm, new); AS-PL A3444S (180 A, freewheel, 6 ribs, 54 mm, new, plug PL_2303); AS-PL A3403S (220 A, freewheel, 6 ribs, 54 mm, new, plug PL_2303) |
|---|---|
| Outputs & variants | Outputs run from 150 A to 230 A. 150 A and 170 A units suit the 518d and 520i four-cylinders; 180 A (Valeo 439709 and 444724, AS-PL A3444S, Ridex 4G0646) is the usual 520d and 525d fitment; 220 A (Hella 8EL 011 713-081, AS-PL A3403S, Ridex 4G0770) and 230 A (Ridex 4G0745, 4G1042, 4G0546, Rotovis 9090865) cover the 530d, 535d, 535i and 550i six- and eight-cylinders. Seven-rib pulleys appear on several of the 220 A and 230 A units, so the rib count is a key check. |
| Genuine (OE) numbers quoted | FG23S032 (AS-PL A3403S), FG23S059 (AS-PL A3141), FG18S052 (AS-PL A3444S), FG18S011 (AS-PL A3469S). |
| Fitment notes | Valeo and Bosch alternators were both fitted and the pulleys differ in rib count (six or seven) and diameter (48 mm to 55 mm), so the old unit must be matched; the Ridex units are supplied without the vacuum pump, and the remanufactured Valeo unit carries a £50.24 core charge refunded on return of the old alternator. |
BMW 5 Series Alternator: Often Blamed on the Battery Instead
On the BMW 5 Series, a failing alternator and a simply weak battery share almost the same symptom set at first: dim lights, sluggish starts, charge that won't hold. Mixing the two up is common, which is why plenty of people replace the battery only to find themselves back at the garage shortly after.
BMW 5 Series Alternator: What It Does
The BMW 5 Series's electrical systems and battery charging both depend on the alternator generating electricity whenever the engine runs. If it's healthy, the battery's job shrinks down to starting the engine and handling brief surges in demand, not powering everything else on its own.
BMW 5 Series Alternator: Watch: Replacing It
Diesel F10/F11; N52 petrol see hLAbbTibxM8
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A Genuinely Useful Finding Worth Knowing on Start-Stop Equipped Models — BMW 5 Series Alternator
If the start-stop system has started behaving erratically, such as failing to engage or re-engage reliably, this is genuinely worth knowing: a struggling alternator is a documented cause of this specific symptom on models fitted with this feature, since the charging system needs to reliably replenish the battery quickly between stops for start-stop to function properly. Newer models fitted with mild hybrid systems and an integrated starter-generator in place of a conventional alternator often need more advanced diagnostic tools to properly identify charging issues, worth knowing this if a specialist mentions needing specific equipment beyond a standard code reader.
It's also genuinely worth knowing that a leaking oil filter housing gasket has been documented as a primary cause of alternator failure on related BMW engines, worth having this checked before assuming the alternator itself is simply worn out.
BMW 5 Series 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 BMW Alternator
The same part, covered across other BMW models.