Second Hand Mercedes-Benz GLS Alternator

The GLS X166 ran from 2016 to 2019, and the updated X167 generation launched for 2020, so a 2017 and a 2020 are from different generations with different engine architectures. Engine codes can differ across that boundary even where the badged engine size looks the same, so always confirm your exact engine code — found on your V5 or a VIN check — before buying. We'd recommend telling the breaker both the engine code and registration so they can verify whether the part crosses that X166-to-X167 boundary safely. Never assume badge-match means part-match across a generation change.

These are different diesel engines — the 350d uses a straight-six OM642 family unit while the 400d uses the newer OM656 straight-six, so the alternators are not the same part despite both being diesel GLS models. Engine code is the decisive factor here, not the badge on the tailgate. Pull your engine code from the V5 or a VIN decoder and give it to the breaker so they can match exactly. Do not assume they interchange because both are diesel six-cylinders in the same body.

Trim level has no bearing on alternator fitment — AMG Line is a styling and equipment package, not a mechanical variant, so the engine underneath is what matters. A GLS 400d AMG Line and a standard GLS 400d with the same engine code use the same alternator. You may find cosmetic differences on parts you can see when removing the alternator, such as engine covers, but the alternator itself is engine-driven, not trim-driven. Give the breaker your engine code and they'll identify the right unit regardless of which trim your car is.

Yes, both 2016 and 2018 GLS models sit within the X166 generation, which ran from 2016 through to 2019, so you're working within the same generation. That said, Mercedes can make ancillary and mounting changes mid-production even within a generation, so confirm with the breaker against your registration and engine code rather than relying on year alone. Supplying your engine code is the most reliable way to get the right match.

Fuel type is a key fitment variable — petrol and diesel engines in the GLS use different alternators suited to each engine's electrical demands and mounting configuration, so a petrol unit will not reliably substitute for a diesel one. Always match the alternator to your specific engine code, not just the vehicle model. Tell the breaker whether your car is petrol or diesel and give them the engine code, and they'll source the correct unit.

The GLS X166 was replaced entirely by the X167 generation in 2020 rather than receiving a mid-cycle facelift in the conventional sense, so the generational boundary here is meaningful mechanically, not just cosmetically. If you're comparing an X166 (2016–2019) alternator with an X167 (2020 onwards), the engine codes are likely different even where the displacement badge appears the same, and ancillary mounting arrangements may have changed. Confirm directly with the breaker using both registrations and engine codes before purchasing, as this is not a boundary we can confirm as safe for interchange.