Mercedes-Benz GLC Alternator: Specs, Fitment & Common Faults
On the GLC, a battery warning light on related models has genuinely been initially quoted at around £420 for a full alternator replacement, but the actual cause was a seized tensioner pulley bearing.
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OEM Part Number: 000-906-79-02-87 (genuine alternator — confirm via VIN) — aftermarket alternators Bosch 0 986 081 850 / Valeo 439941
| Alternators (aftermarket) | Bosch 0 986 081 850 (175 A, freewheel pulley, 6 ribs, 52.5 mm, remanufactured exchange, plug PL166, core charge £23.51, excludes vacuum pump); Bosch 0 986 084 980 (200 A, rigid multi-rib pulley, 6 ribs, 50 mm, remanufactured exchange, plug 125, core charge £24.11, excludes vacuum pump); Bosch 1 986 A01 045 (130 A, freewheel pulley, 6 ribs, 52.5 mm, new, plug 125, excludes vacuum pump); Valeo 439941 (200 A, 6 ribs, 50 mm, new original); Valeo 440685 (200 A, 6 ribs, 51 mm, remanufactured exchange, core charge £50.24); Hella 8EL 011 713-761 (200 A, rigid V-ribbed pulley, 6 ribs, 50 mm, new); Lucas LRA03818 (200 A, rigid multi-rib pulley, 6 ribs, 50 mm, remanufactured, plug 0239 LIN2, core charge £25.12); Ridex 4G0522 (200 A, rigid multi-rib pulley, 6 ribs, 50 mm, new, excludes vacuum pump). |
|---|---|
| Outputs & variants | 200 A six-rib 50 mm units (Valeo 439941 pattern) are the main fit for the OM651 2.2 diesel GLC 220 d/250 d and M274 petrol GLC 250/300; 175 A six-rib 52.5 mm freewheel units suit lower-spec petrols; 250 A units cover the OM654 2.0 diesel; the EQ Boost 48 V mild hybrids are not covered. |
| Genuine (OE) numbers quoted | CG20U015 (AS-PL A3361S); 439941 (AS-PL A3361(VALEO) and Valeo 439941); FG18T162 (AS-PL A3575S); 439991 (AS-PL A3669(VALEO)); 439895 (AS-PL A3363(VALEO) and Valeo 439895). |
| Fitment notes | The GLC shares its alternators with the W205 C-Class, so the Valeo OE number on the old unit is the surest match; all engines have start-stop and a LIN-controlled alternator, and exchange units from Bosch, Valeo and Lucas carry core charges of £23-£50. |
Mercedes-Benz GLC Alternator: Often Blamed on the Battery Instead
Because a weak Mercedes-Benz GLC battery and a dying alternator both cause dim lights, slow starts and charge that won't hold, it's an easy mistake to replace the wrong one first. That mix-up sends plenty of people back to the garage a few weeks later, the real fault still there.
Mercedes-Benz GLC Alternator: What It Does
Every time the Mercedes-Benz GLC's engine runs, the alternator is generating the electricity that charges the battery and directly feeds the electrical systems. A properly working alternator leaves the battery mostly responsible for engine starts and short demand spikes — not for running the electronics unaided.
Mercedes-Benz GLC Alternator: Watch: Replacing It
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A Genuinely Alarming, Honest Real Account Worth Knowing — Mercedes-Benz GLC Alternator
If the battery warning light has come on, this is genuinely worth knowing before paying for a full alternator replacement: a battery warning light on related models has, in documented cases, been initially quoted at around £420 fully fitted for a complete alternator replacement, but the actual root cause turned out to be a seized tensioner pulley bearing rather than a genuine alternator failure. Once this bearing loses its lubrication, the drive belt begins sliding and eventually destroys itself, stopping the alternator being driven entirely and triggering the same warning light, even though the alternator itself is completely fine.
It's also genuinely worth knowing that the pulley driving the alternator on many of these engines is a genuine one-way clutch mechanism, allowing the alternator's rotor to coast down gently to a stop rather than being abruptly halted.
Mercedes-Benz GLC 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 Mercedes-Benz Alternator
The same part, covered across other Mercedes-Benz models.