The MAHLE effect to counter alternator failure

What should you keep in mind when replacing the alternator? Here in a nutshell is everything you need to know.

Uncovered is already half the job done—grab leaks by the collar

Oil residue in the alternator
Oil residue in the alternator

Just like with other components in the engine compartment, it is important to check the area. This will usually help track down the cause of the defect quickly. First clue: oily residue! This immediately tells you that something is wrong here.

But how does engine oil even get into the alternator? Serious defects often have a simple cause: a small leak in the cylinder head area, or just carelessness when adding engine oil or changing the oil filter.

And the damage is already done: increased brush sparking and increased wear, overheating of the voltage regulator, and the brushes seize up.

The oil and carbon dust bond together to form a slurry-like mass and become electrically conductive. When the “slurry” builds up between the slip rings on the rotor and the alternator housing, sooner or later there will be a short circuit!

Severe wear on the slip rings and carbon brushes
Severe wear on the slip rings (left) and carbon brushes (right)


  • Always cover the alternator with a rag when changing the oil filter.
  • (For tips on how to change the oil filter, go to:
  • Track down and fix any leaks in the engine, fuel system, or hydraulic system.
  • Always thoroughly clean up engine oil, diesel, and hydraulic residues.

Alternators for heavyweights, too

generator +

Starting immediately in the MAHLE Aftermarket product range: 23 new alternators in OE quality for the ten largest manufacturers of heavy-duty commercial vehicles. But that’s not all—we have plans to offer alternators for 80% of all commercial vehicle applications in the future.

Find the right MAHLE Original alternator here: Link


We regularly provide technical tips relating to the powertrain, thermal management, and mechatronics in automobiles.


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