Car Alternator Problems

The modern cars, trucks and caravans are well-equipped with every comfort one can imagine. All these appliances and engine however need loads of electric power to operate. Where does all this power come from? This need is taken care of by a very simple gadget called the alternator. It is short for alternating current generator. Through the use of the alternator, which is a dynamo, your car generates its own power and stores it by charging the battery. Thus the chemical energy of the fuel in your tank is converted into electrical energy. The efficiency of these devices is around 50 - 60%.

It is absolutely essential that you keep a check on the working of the alternator or you may be left high and dry with no power to drive your car!

How Does the Car Alternator Work?

The alternator creates electricity by exploiting a fundamental law of electromagnetism which is, changing magnetic field creates an electric field! There are two important parts of the alternator, the stator and the rotor. The rotor is essentially a set of three pairs of electromagnets with opposite poles facing each other placed on a cylindrical circular disc, 120 degrees out of phase from each other. Stator is the stationary part placed at the centre of the rotor disc.

The rotor is attached to the crankshaft of the engine by a belt. Therefore as the engine is operational, the crankshaft rotation starts the rotation of the alternator rotor. The revolving rotor creates a changing magnetic field that induces a current in the central stator. A current is generated 120 degrees out of phase by each of the magnet pairs. There are output terminals attached to the stator with separate windings for every phase.

This current obtained however is an AC current but the car accesories require DC current for operation. Therefore, alternating current to direct current conversion is achieved by connecting the output current from the stator to a double bridge rectifying diode circuit which effectively does the job. So, one car alternator with such three sets of magnets generates a threefold current which is 120 degrees out of phase. The total voltage output of the alternator is around 14 V typically.

The d.c. output from the rectifier is fed to the battery which gets charged and it effectively 'stores' the generated electricity. For operating the electromagnets in the alternator, a voltage needs to be supplied from the battery at the start which is called 'exciter' voltage. The whole alternator assembly is supported by bearings for smooth rotation.

Car Alternator Problems

Any piece of electromechanical equipment is bound to breakdown at some point, if not maintained properly, due to the constant frictional forces. Keeping a tab on the performance of your car alternator and maintaining it is a simple job. Let us have a look at all the things that could go wrong and how we could rectify them or prevent them.

Firstly, observe that on the front panel of your car, there is a light or LED that glows at ignition. It is the indicator that the 'exciting' voltage required by the alternator is being applied. If it is not glowing, it means that the voltage feedback mechanism from the battery to the alternator is messed up or the LED needs to be replaced. If it's the former, get the feedback mechanism checked.

The alternator has three operating stages, each giving a certain voltage output. Therefore even if one stage or two stages fail, you may not notice as some amount of voltage output is still charging the battery. Also, if you are not putting a lot of load on the battery, and all three stages have failed, still the car can operate on the reserve charge in the battery.

The way to check out this problem and take care of it is quite simple. Set the engine on idling mode and check the voltage between the output terminals of the alternator by using a digital multimeter set on the voltage mode. If it has fallen below the maximum of 14 V, then there may be a stage failure. In case it is indeed maximum at 14 V, check if it remains stable after you apply more load like the air conditioning. If it is not remaining stable, you must take the alternator for repair.

Check if the electromagnets are operational by seeing if metal objects get attracted towards the alternator. Then check for unusual rumbling noise from the alternator. It may indicate that the bearings are wearing out. In that case, you may need to replace them soon. Check the rotor belt as it may slip or break. Replacements are easily available at your neighborhood car accessories store.

Last but not the least, have a tried and trusted mechanic by your side for expert advice in case the symptoms of the problem go beyond your understanding. Always try to understand a car problem if it crops up, even if the mechanic solves it for you. Trust me it always helps!