Car generator defects: facts and DIY manual!

Car generator defects: facts and DIY manual!

The generator (or dynamo/alternator) converts the mechanical engine energy into electric energy, charging the battery and keeping it charged even when headlights, radio and seat heating are on. A defective generator can quickly become a problem, since the ignition is started via the battery.

The generator in detail

car engine generator in detailThe generator is not a wear part. Modern alternators have a very long life span and hardly ever break down.

Nevertheless, damage and defects can occur in any component. In this case, it is better to replace the generator rather than repairing it.

Tell-tale signs of a generator defect

There are several tell-tale signs of a possible generator defect. Should one of those signs occur, the generator must be checked right away.

  • A first sign is start difficulties, meaning several attempts are necessary to get the engine running.
  • Another sign is a discharging battery. If a new battery discharges soon after installation, this is generally due to an alternator defect.
  • If the battery light on the dashboard is on, there might be a problem with the dynamo as well.

Possible defects

A generator and the connected power supply have four weak points where most defects occur. These are:

1. The dynamo itself
2. The charge regulator
3. Cables and plugs
4. V-belt

1. The generator

car generator defectsIf the generator is failing, very likely the carbon brushes are used up. This can only be remedied by complete replacement of the generator.

2. The charge regulator

alternator defects due to charge regulatorVery often, the charge regulator is responsible for alternator defects. It regulates the electricity flow from the generator. If it is malfunctioning, the component can only be adequately checked and maintained in a garage. In most cases, replacement is the only solution.

3. Plugs and cables

Cables and plugs of alternatorCables and plugs connecting alternator and battery can have defects. A ruptured or worn cable could weaken or even interrupt the power supply.

4. V-belt

dynamo V-belt is worn outIf the V-belt is worn or slack, the power flow between alternator and engine is weak. The generator is not defective, but no longer capable of receiving kinetic energy from the engine.

Garage or DIY replacement?

generator replacementReplacing a generator is not a simple task any layman can perform. Particularly in view of the many different damage factors consulting a garage is recommended. This is, of course, always a budget matter. In a garage, replacement of a dynamo, including the spare part, costs up to EUR 800 (± £700) or more.

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Step by step replacement of a generator

Replacing a generator differs depending on car. Reason for this lies in the various constructions of engines and engine compartments. First, the alternator has to be found in the engine compartment. Thus the steps may vary.
Step by step replacement of a generator

  •  disengage the battery
  •  find the generator
  •  if necessary, remove the cover
  •  remove other parts if they are blocking access to the generator
  •  loosen the V-belt tensioner
  •  remove power and earth cables from the generator
  •  unscrew and remove mounting bolts
  •  remove the generator.
  •  compare the new generator on sight with the old one.
  •  perform all disassembly steps in the reverse order. Mind the prescribed tightening torque and belt tension.

Avoid the following errors

Error when removing the alternator

  • When disassembling the dynamo it is important to remember which connections are located where. If necessary, document the disassembly with pictures and mark the individual components.
  • These delicate operations in the engine require the utmost care. Always mind the proper bolt tightening torques.
  • The spare part must be installed safely and securely and may not become loose by engine movements. The same applies to the V-belt tension. Here also exact instructions apply which need to be followed.

Foto: Philip Lange, BLKstudio, hkhtt hj, yanik88, ekapotfotothai, Heikki Wichmann, Tatchaphol, WPixz, Mr.1, Phanat /

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