Audi A1 Alternator: Specs, Fitment & Common Faults
A genuinely important, confirmed finding: 48V mild hybrid alternator failure has been documented with a US extended warranty, though UK owners have found it harder to get equivalent support.
Illustration for editorial purposes
Opens live listings in a new tab.
OEM Part Number: 04E903023K (genuine alternator — confirm via VIN) — aftermarket alternators Bosch 1 986 A00 902 / Valeo 439664
| Alternators (aftermarket) | Bosch 1 986 A00 902 (140 A, freewheel pulley, 6 ribs, 56.2 mm, new, plug ID 61, B+ M8, excludes vacuum pump); Bosch 0 986 081 160 (140 A, freewheel, 6 ribs, 55.9 mm, remanufactured exchange, COM plug ID 166, core charge £92.39, excludes vacuum pump); Bosch 0 986 045 340 (140 A, freewheel, 6 ribs, 56.2 mm, remanufactured exchange, plug PL61 with L/DFM, core charge £100.47); Valeo 439664 (150 A, freewheel, 6 ribs, 57 mm, new, B+ clamp, four-point mounting); Valeo 437454 (150 A, freewheel, 6 ribs, 57 mm, remanufactured exchange, core £50.79); Hella 8EL 012 430-291 (140 A, freewheel, 6 ribs, 56 mm, new, B+ and LIN connector); Lucas LRA02291 (140 A, freewheel, 6 ribs, 56 mm, remanufactured, plug 0121 with M8 B+ and L-DFM, core £25.12); AS-PL A0429S (140 A, freewheel, 6 ribs, 49 mm, new, plug PL_2306) |
|---|---|
| Outputs & variants | Three outputs are listed. 110 A units (Ridex 4G0802, 4G0740, 4G0107, AS-PL A0181PR) use the simple L/DFM two-wire plug and suit the smaller petrol engines; 140 A is the most common fitment and splits between COM/LIN-controlled units (Bosch 0 986 081 160, Hella) and L/DFM units (Bosch 0 986 045 340, Lucas); 150 A Valeo units (439664, 437454, Ridex 4G0157) are the higher-output option typically fitted to diesel and higher-spec cars. Almost every reference carries a freewheel (overrunning) pulley; the only rigid-pulley options are the 110 A Ridex 4G0740 and AS-PL A0181PR. |
| Genuine (OE) numbers quoted | 0124525530 (quoted against AS-PL A0429S); none quoted for the other references. |
| Fitment notes | Pulley diameter varies between 49 mm and 57 mm across the listed units, so the old pulley should be measured before ordering; the Bosch and Ridex units are supplied without the vacuum pump, so the original pump must be transferred where fitted, and the remanufactured Bosch, Valeo and Lucas units carry a core charge refunded on return of the old alternator. |
Audi A1 Alternator: Often Blamed on the Battery Instead
On the Audi A1, 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.
Audi A1 Alternator: What It Does
Running the Audi A1'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.
Audi A1 Alternator: Watch: Replacing It
diagnosis-led 8X video; no dedicated full A1 swap video found in 3 searches
Opens live listings in a new tab.
A Genuinely Important, Confirmed Finding Worth Knowing on the Mild Hybrid System — Audi A1 Alternator
If your car is fitted with the 48V mild hybrid system, this is genuinely important to know: alternator failure specifically related to this system has been directly documented among owners, with the US having confirmed an extended warranty covering this exact issue. UK owners have found it genuinely more difficult to get equivalent support from Audi UK for the same underlying fault.
It's also genuinely worth knowing that going through more than one battery in a short period is a strong sign the alternator isn't charging properly, worth testing its actual voltage output directly with a multimeter.
Audi A1 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 Audi Alternator
The same part, covered across other Audi models.