Bosch Mercedes-Benz M111 W202 W124 Alternator 0986039860 - Used Original Parts

Quick Answer

This alternator is the right fix when a W202 C-Class or W124 E-Class with the M111 four-cylinder engine shows a charging warning light, a battery that keeps going flat, or a failed output test, and the battery and belt have already been ruled out. A tested Genuine used Bosch unit suits these cars because the original-spec build is hard to match with budget aftermarket rebuilds, and the car is usually old enough that a full new unit is hard to justify. In Malaysia's heat, humidity and stop-go traffic, a proven working original gives dependable charging at a sensible cost.

Diagnosis and Common Symptoms

The M111 W202 and W124 cars use a belt-driven Bosch alternator with an internal regulator. Wear is mostly in the carbon brushes, slip rings, rectifier diodes and front bearing. Malaysian heat and short trips speed this up.

Typical symptoms:

• Red battery warning light on the instrument cluster, either steady or flickering at idle.
• Dim headlights or a slow-turning blower fan, especially at idle with the A/C on.
• Battery repeatedly flat or weak after short drives, even when the battery tests fine.
• Whining, grinding or rumbling from the front of the engine, which points to a worn alternator bearing.
• Belt squeal on start-up or when the electrical load rises.
• Rough idle, hesitation or stalling caused by low system voltage upsetting the ignition and injection electronics.
• Burning smell or excessive heat from the alternator body, which suggests rectifier or winding failure.

These are older Mercedes platforms, so there is usually no specific fault code for the alternator itself. On later W202 cars with diagnostic support, low-voltage entries may appear in other modules. Do not condemn the alternator on the warning light alone.

Check the following before replacing it:

1. Measure battery voltage with the engine off. A healthy battery reads about 12.4–12.7 V.
2. Measure at the battery with the engine running at about 2,000 rpm. A healthy charging system reads about 13.8–14.5 V.
3. Switch on the headlights, blower and rear demister, then recheck. Voltage should hold steady.
4. Inspect the belt, tensioner and pulley for slip, cracking or play.
5. Check the battery terminals and the earth straps for corrosion and poor connections.

Introduction

This Bosch alternator is a Genuine used original unit taken from a Mercedes-Benz M111 W202 or W124 donor car. Every unit is bench or vehicle tested for correct charging output before it is listed, so it is a proven working part and not an untested pull. You get the original Bosch build quality and fitment of the factory unit at a fraction of the cost of new. It is a practical, dependable choice for keeping an M111 W202 or W124 reliably on the road.

Product Details

• Brand: Bosch

• Model Compatibility: Mercedes-Benz M111 engine, W202 C-Class and W124 E-Class (verify by part number)

• Part Name: Alternator (Generator)

• Condition: Genuine Used (Tested Working)

• Notes: Compare the Bosch part number and amperage rating on the alternator body with your old unit before ordering, as output and pulley type vary by model and options. Check the pulley, mounting lugs and electrical connector for a match. Replace the drive belt and inspect the tensioner at the same time, since a worn belt or tensioner will shorten the life of any alternator. Disconnect the battery before removing or fitting. No coding or programming is needed after installation.