What is an Alternator
An alternator is a device which uses a rotor and a stator along with diodes to convert mechanical energy to electrical energy and gives output in form of alternating current .This current is converted to direct current and is used to charge the battery of your car. The battery starts the alternator after which the battery is again charged using the alternator continuously. So, if the alternator goes bad the battery will die out after travelling some miles and the result will be a breakdown.

Locate the Alternator
As you flip open the bonnet of your car, your battery and the alternator will be visible clearly. It has a pulley and a belt attached to it.

To check whether the alternator is charging the battery properly

  • You should turn off the ignition of your vehicle and use a voltmeter to test the battery. It should read 12.2 Volts or higher. This is the minimum voltage needed to start the alternator. Any voltage lower than 12.2 Volts will not be able to start the alternator and further testing should be carried out only when you get a charged battery.
  • The light on the battery should not be on. If it is, there might be a problem with the alternator.
  • You can check with the brightness level of the headlights when you accelerate the engine without putting the car in any gear. As the RPM meter shows higher reading, the headlights should go brighter. If they are still dim even after turning the brightness dial to the maximum, there is a problem with the alternator.
  •  Also recheck the battery with a voltmeter. The alternator is working properly if it reads between 13.5 to 14.5 Volts. If the voltage stays constant or goes low, your alternator is the culprit.
  • While starting the engine, the alternator pulley should spin properly and should not slip. Also if it looks shiny and there are visible cracks, you should change the belt. Only if the alternator is spinning smoothly, it can send proper energy to the battery.
  • You can also try to listen to the sound that comes from the alternator when the engine is running. If you hear a strange sound which becomes more intense when more electrical systems use the battery, there is a small problem with the bearings of the alternator. You can get it fixed by a mechanic.
  • You can try and touch the alternator after running the engine for a while. If the temperatures are too high, this is a signal that it may break down soon. Most probably the insulation of the windings is worn out. You should go see a mechanic.


While testing your alternator’s performance you should keep the following points in mind


  • Do not attempt to remove any cables from the battery or the alternator while the engine is running. It can damage your computer and other electrical systems. Always use a voltmeter to check the connection. It always is safe and accurate.
  • It is advisable not to touch the battery and the charging systems. Be extra careful when you do so.
  • Do not cross connect any cables to check the output of any charging equipment. It can blow your charging system.
  •  Do not use any metal body directly in contact or your finger ring for example to complete any sort of circuits and check for current flows. It can be dangerous.


If you are still unable to get to the roots of the problem, you can always get your charging set checked by a motor mechanic.