Fiat 500 (Petrol) Alternator: Specs, Fitment & Common Faults

On the classic petrol 500, a genuinely useful DIY access technique helps reach the notoriously awkward top mounting bolt when replacing the alternator.

Generation covered: this guide is for the classic petrol/hybrid 500 (2007–2024) — not the fully electric 500e (2020–present), which is a completely different car sharing no mechanical parts despite the similar styling. Check your logbook or VIN, or confirm whether your car has an engine or an electric motor, if you're unsure which one you have.

Illustration for editorial purposes

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OEM Part Number: 51859041 (genuine alternator — confirm via VIN) — aftermarket alternators Bosch 0 986 048 771 / Denso DAN517

Accuracy note: Covers the Fiat 500 (Petrol) (2007- petrol 500) 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)	Denso DAN517 (70 A, multi-rib rigid pulley, 5 ribs, 54 mm, new); Denso DAN519 (90 A, multi-rib rigid pulley, 5 ribs, 54 mm, new); Denso DAN1078 (120 A, freewheel pulley, 5 ribs, 54 mm, new); Denso DAN999 (120 A, multi-rib rigid pulley, 5 ribs, 54 mm, new); Bosch 0 986 048 771 (90 A, freewheel pulley, 6 ribs, 54 mm, reman exchange, M8 B+ and M5 D+ terminals, excludes vacuum pump, £100.47 surcharge); Lucas LRA02804 (90 A, freewheel pulley, 6 ribs, 54 mm, reman, plug 0230, M8 B+ and M5 D+ terminals, £20.09 surcharge); AS-PL A4083 (120 A, freewheel pulley, 5 ribs, 54 mm, new, plug PL_9104); Ridex 4G0036 (70 A, rigid pulley, 5 ribs, 55 mm, new, B+ M8 and D+ M5 terminals, excludes vacuum pump)
Outputs & variants	65 and 70 A units with 4- or 5-rib rigid pulleys are the basic 1.2 8v petrol fitment; 90 A units in 5-rib rigid (Denso DAN519) and 6-rib freewheel (Bosch, Lucas, Ridex 4G0030) forms cover the 1.2 and 1.4 petrol with higher load and the 1.3 Multijet diesel; 105 to 120 A units (Ridex 4G0845, Denso DAN1078, DAN999, AS-PL A4083) serve the 0.9 TwinAir and air-conditioned 1.4 cars; a 150 A Ridex 4G0194 with a 78 mm pulley is listed for the heaviest-load fitment.
Genuine (OE) numbers quoted	51859041 (genuine alternator number for this model — confirm via VIN, as outputs differ by engine)
Fitment notes	The 500 uses D+ (M5) and B+ (M8) screw terminals rather than a multi-pin plug on most units, and the pulley varies between 4-, 5- and 6-rib and between rigid and freewheel types, so the old unit must be matched on rib count and pulley before amperage. Bosch and Ridex references exclude the vacuum pump. The Bosch reman carries a £100.47 surcharge, the Lucas £20.09 and the Ridex 4G0036R £27.13; AS-PL PR units are exchange without a deposit.

A Genuinely Useful, Real DIY Access Technique Worth Knowing — Fiat 500 (Petrol) Alternator

If you're replacing the alternator yourself and struggling to reach the top mounting bolt, this is genuinely worth knowing: disconnecting the "dog bone" engine mount and wedging the engine forward slightly, away from the firewall, creates just an extra inch of working space — but that single extra inch has been described as making all the difference when trying to reach this specific bolt on related models.

A genuinely useful diagnostic technique worth knowing: pressing one end of a long screwdriver against the alternator housing and the other end near your ear, similar to a stethoscope, can help isolate whether noise is genuinely coming from the alternator itself.

It's also genuinely worth knowing it's worth briefly running the engine with the auxiliary drive belt removed, if safe and practical, since this rules out the belt itself as the source of a noise you might otherwise blame on the alternator.

Fiat 500 (Petrol) Alternator: Watch: Replacing It

🎬 Watch: How to Replace the Alternator on a Fiat 500 1.4 16v 1.2 8v

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Covers both the 1.2 8v and 1.4 16v petrol 500.

Fiat 500 (Petrol) Alternator reference plate

Fiat 500 (Petrol) Alternator: Often Blamed on the Battery Instead

On the Fiat 500 (Petrol), 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.

Fiat 500 (Petrol) Alternator: What It Does

Electricity generation while the Fiat 500 (Petrol)'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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Fiat 500 (Petrol) 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 Fiat Alternator

The same part, covered across other Fiat models.