Autopapyrus · Mercedes-Benz A-Class W176 1.6 M270 (2017)
https://autopapyrus.com/guides/mercedes-benz/a-class/alternator-replacement/

Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Mercedes-Benz A-Class W176 1.6 M270 (2017): Alternator Replacement

On the Mercedes A-Class W176 with the M270 1.6 engine, the alternator is located at the front of the engine bay on the right (driver's side in left-hand-drive cars). Replacement requires removing the serpentine belt and reaching the mounting bolts: two upper and two lower (E12 Torx or 13 mm socket). The job is of medium difficulty because of the limited space in the engine bay.

Difficulty: Medium Time: 1.5-2 hours Steps: 16 Tools: socket set (10 mm, 13 mm, E12 Torx), open-end wrenches 13 mm and 17 mm, ratchet with extension, pry bar or special belt tensioner tool, flashlight, jack and jack stands (for access from below)

Part

🔩 12V 150A alternator (OE numbers A0009060022 or A0009061903, aftermarket equivalent Bosch 0124615030)

There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes and 7 more. See manuals →

Step by step

16 steps

Disconnect the negative battery terminal with a 10 mm wrench and wait 5-10 minutes to let the system discharge any residual voltage.
Remove the decorative engine cover (if fitted) by pulling it up and toward you. The clips are plastic.
Take a photo of the serpentine belt routing diagram (the sticker is usually on the upper crossmember or the radiator cover).
Release the belt tensioner: rotate the tensioner pulley counterclockwise with a 17 mm wrench or a special belt tensioner tool, then take the belt off the pulleys.
Disconnect the electrical connector on the alternator housing (press the locking tab and pull it toward you).
Remove the protective cap from the alternator's positive terminal, undo the 13 mm nut, and remove the power cable.
Remove the two upper alternator mounting bolts (E12 Torx or 13 mm socket). They are accessible from above through the engine bay.
To reach the lower bolts, raise the front of the car with a jack, support it on jack stands, and remove the lower engine undertray (if fitted). It is held by 4-6 10 mm bolts or clips.
Remove the two lower alternator mounting bolts from underneath (E12 Torx or 13 mm socket). Use an extension and a ratchet.
Take the alternator out of the engine bay. It is usually easier to pull it out downward through the wheel arch area, or upward by sliding it toward the front of the car (this depends on the layout of the accessories).
Install the new alternator in reverse order. Start the lower bolts first, then the upper ones, and tighten them to 20-25 N·m (15-18 lb-ft) (check the exact value in the manufacturer's service manual).
Connect the power cable to the positive terminal, tighten the 13 mm nut to 10-12 N·m (7-9 lb-ft), and refit the protective cap.
Plug in the electrical connector until the locking tab clicks.
Install the serpentine belt following the routing diagram (first onto all the pulleys except the tensioner, then rotate the tensioner and slip the belt onto the tensioner pulley).
Refit the engine undertray and the decorative engine cover, then reconnect the negative battery terminal.
Start the engine and check for unusual noises. The battery warning light on the instrument cluster should go out within 2-3 seconds.

Common mistakes and warnings

Do not let oil or coolant get on the new alternator. Check the condition of the seals and hoses before installation. The mounting bolt torque is critical: under-tightening causes vibration and premature bearing wear, while over-tightening distorts the housing. If you replace the belt at the same time as the alternator, check the tensioner and idler pulleys for play and noise. Their service life is usually 80,000-100,000 km (50,000-60,000 miles).