Volkswagen Up! Alternator: Specs, Fitment & Common Faults
On the Up!, a chattering noise at idle is often the overrunning alternator decoupler pulley, not the alternator itself failing — a genuinely well-documented VW/Audi Group weak point.
Illustration for editorial purposes
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OEM Part Number: 04E903023K (genuine alternator — confirm via VIN) — aftermarket alternators Bosch 1 986 A01 073 / Valeo 440674
| Alternators (aftermarket) | Bosch 1 986 A01 073 (110 A, rigid multi-rib belt pulley, 6 ribs, 49.5 mm, new, plug type 61, excludes vacuum-pump engines, 170 mm long); Bosch 1 986 A01 069 (110 A, freewheel clutch pulley, 6 ribs, 49.5 mm, new, plug type 125, excludes vacuum-pump engines, 175 mm long); Bosch 0 986 083 270 (110 A, freewheel clutch pulley, 6 ribs, 53.5 mm, remanufactured exchange with £24.38 core charge, PL166 single-pin plug, excludes vacuum-pump engines, 191 mm long); Bosch 1 986 A01 246 (140 A, freewheel clutch pulley, 7 ribs, 52.3 mm, new, plug type 181, excludes vacuum-pump engines, 202 mm long); Hella 8EL 011 713-391 (110 A, freewheel clutch pulley, 6 ribs, 49 mm, new); Hella 8EL 011 713-681 (110 A, freewheel clutch pulley, 6 ribs, 50 mm, new); Hella 8EL 015 630-981 (110 A, rigid belt pulley, 6 ribs, 50 mm, new); AS-PL A0852S (110 A, freewheel clutch pulley, 6 ribs, 52 mm, new, PL_2306 plug) |
|---|---|
| Outputs & variants | 110 A is the standard output for the 1.0 petrol engines and accounts for most of the listings. 90 A units (BV PSH 305.931.090.010 and 305.931.090.280, AS-PL A0917(SEG), A01402(SEG) and A01403(SEG)) cover the lowest-specification cars, and 140 A and 180 A units (Bosch 1 986 A01 246, AS-PL A0310, BV PSH 305.906.140.000, Hella 8EL 011 713-831, Valeo 440674) cover the higher-load specifications. The 110 A units are offered with both rigid (Bosch 1 986 A01 073, Hella 8EL 015 630-981, AS-PL A0527PR) and freewheel clutch pulleys, in diameters from 49 mm to 53.5 mm, with plug types ranging across type 61 (L/DFM), 125, 166 and 181 (COM/LIN). |
| Genuine (OE) numbers quoted | TG12C280 (AS-PL A3370S); F000BL0701 (AS-PL A0852S); 0124525200 (AS-PL A0310); F000BL04K7 (AS-PL A0917(SEG)); F000BL04R7 (AS-PL A01403(SEG)); F000BL04L7 (AS-PL A01402(SEG)). |
| Fitment notes | Several different 110 A units were fitted over the production run, differing in pulley type, pulley diameter and plug, so the unit coming off must be matched for all three rather than just the output. Rigid-pulley and freewheel-pulley units are not interchangeable on the same belt run. All Bosch units exclude engines with an alternator-driven vacuum pump. The Bosch 0 986 083 270 exchange unit carries a £24.38 core charge and the Valeo 440674 a £50.24 core charge, refunded on return of the old unit; the AS-PL exchange units need no deposit. |
Confirmed: A Chattering Noise at Idle Is Often the Decoupler Pulley, Not the Alternator — Volkswagen Up! Alternator
A genuinely well-documented VW/Audi Group weak point spans decades of models: the overrunning alternator decoupler (OAD), sometimes called an overrunning alternator pulley (OAP) — a freewheel clutch pulley designed to reduce vibration transmitted through the drive belt. When it starts to fail, it produces a distinctive chattering or rattling noise specifically at idle, often making the belt tensioner visibly vibrate too, and this is frequently mistaken for a failing alternator or a worn belt when the alternator itself is usually still perfectly healthy.
Worth knowing when sourcing a replacement: VW used both Bosch and Valeo as original alternator suppliers, and while both do the same job, they're not always directly interchangeable due to differences in pulley design and electrical connectors — always confirm which brand and amperage your specific car has (usually printed on a sticker on the alternator body) before ordering, and stick with a replacement from the same original supplier where possible.
Volkswagen Up! Alternator: Often Blamed on the Battery Instead
On the Volkswagen Up!, it's genuinely hard to tell a weak battery from a failing alternator just from symptoms — both produce dim lights, slow starts, and a battery that won't hold charge. That's exactly why so many people end up replacing the wrong part, then returning to the garage a few weeks later.
Volkswagen Up! Alternator: Watch: Replacing It
same small VW petrol layout; the up! alternator sits in the same place
Volkswagen Up! Alternator: What It Does
Running the Volkswagen Up!'s electrical systems and keeping the battery charged while the engine turns over — that's the alternator's role. A properly functioning one means the battery only really needs to worry about starting the car and absorbing occasional spikes in demand.
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Volkswagen Up! 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 Volkswagen Alternator
The same part, covered across other Volkswagen models.