Ford Focus Mk3 Alternator: Specs, Fitment & Common Faults
The simple multimeter test that confirms whether it's genuinely the alternator — plus why some replacement units develop the exact same fault.
Illustration for editorial purposes
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A Simple Test to Confirm the Alternator Before Replacing It
Before paying for a replacement, it's worth confirming the alternator is genuinely the problem: 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 suggest a failing voltage regulator, a related but different fault. A whining noise that gets noticeably louder when heavy electrical loads switch on (headlights, heated rear window, air conditioning on full) is also a strong practical indicator worth checking before assuming the worst.
Ford Focus Mk3 Alternator: Often Blamed on the Battery Instead
On the Ford Focus Mk3, a weak battery and a failing alternator produce almost identical symptoms at first — dim lights, slow starts, a car that won't hold charge — which is exactly why so many people replace the battery, only to be back at the garage a few weeks later with the real culprit untouched.
Ford Focus Mk3 Alternator: Watch: Replacing It
Mk3; also 5oUHGsYKcHE (2012-14 Mk3 2.0) and F-NDmj667Tg
OEM Part Number: CV6Z-10346-B (genuine alternator — confirm via VIN) — aftermarket alternators Bosch 0 986 082 220 / Valeo 440688
| Alternators (aftermarket) | Bosch 0 986 082 220 (120 A, rigid multi-rib pulley, 6 ribs, 49 mm, reman exchange, PL174 plug with B+ M8 and LIN, 176 mm long, excludes vacuum pump, core charge GBP 23.51); Bosch 0 986 084 230 (150 A, freewheel clutch pulley, 6 ribs, 54 mm, reman exchange, PL174 plug with B+ M8 and LIN, double pivot mounting, 192 mm long, excludes vacuum pump, core charge GBP 47.03); Valeo 440688 (150 A, V-ribbed pulley, 6 ribs, 54 mm, reman premium exchange, M8 and COM, four-point mounting, L40 position, core charge GBP 50.24); Valeo 439906 (150 A, freewheel clutch pulley, 6 ribs, 55 mm, new, B+, four-point mounting, L80 position); Valeo 440575 (120 A, freewheel clutch pulley, 6 ribs, 55 mm, reman exchange, B+, L40 position, core charge GBP 48.42); Hella 8EL 015 630-121 (120 A, freewheel clutch pulley, 6 ribs, 54 mm, new, core charge GBP 6.91); Hella 8EL 015 630-091 (120 A, V-ribbed pulley, 6 ribs, 49 mm, new); Lucas LRA03470 (150 A, freewheel clutch pulley, 6 ribs, 54 mm, reman, plug 0213 with M8 B+ and COM/LIN2, core charge GBP 25.12) |
|---|---|
| Outputs & variants | Two outputs cover the range, 120 A and 150 A. The 120 A units come either with a 49 mm rigid pulley (Bosch 0 986 082 220 pattern, mainly 1.6 Ti-VCT petrol) or a 54 to 55 mm freewheel pulley; the 150 A units are all freewheel clutch pulley at 51 to 55 mm and serve the EcoBoost petrols and TDCi diesels with higher electrical load. Valeo units are also distinguished by regulator plug position, L40 against L80. |
| Genuine (OE) numbers quoted | AS-PL A3267S quotes TG15C186; AS-PL A3129 quotes TG12C087; AS-PL A3259 quotes TG12C145; AS-PL A3666S quotes FG15T101. |
| Fitment notes | The pulley diameter matters as much as the amperage, with 49 mm, 51 mm, 54 mm and 55 mm all offered, so measure the old pulley before ordering; freewheel clutch pulleys should be replaced like for like and never swapped for a rigid pulley on a car that had one; the Bosch, Valeo and Lucas exchange units carry a core charge that is refunded when the old alternator is returned; the Bosch and some Ridex units are marked as excluding engines with an alternator-driven vacuum pump. |
The Mk3 Focus most commonly used a 120-amp alternator for standard-spec petrol models, with a 150-amp unit reserved for higher electrical loads. Diesel and ST variants use different mounting configurations entirely, so always cross-check the physical connector and pulley type as well as the part number.
Ford Focus Mk3 Alternator: What It Does
The Ford Focus Mk3's alternator generates electricity while the engine runs, charging the battery and powering the car's electrical systems directly. A healthy alternator means the battery is mostly there for starting the engine and covering brief demand spikes — not for actually running the car's electronics on its own.
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Ford Focus Mk3 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.