While your engine is running or while driving and your battery warning light starts glowing on the instrument panel, you may have a battery charging problem. 

If your battery is frequently going dead or you find your engine is cranking slowly before your engine starts, you may have a charging problem also. Likewise, if the voltage or current (amps) gauge is giving a low reading that too might indicate a charging problem.

Here is a quick way to check the charging system of your car.  Start the car and turn on the headlights. Dim lights indicate that the lights are running off the battery.  It also means that too little current or no current is produced by the alternator.  As you speed up the engine and the lights get brighter, it means that the alternator may be producing a little current but not enough at idle speed so as to keep the battery charged properly.  However, your charging system would be functioning properly when you increase the engine speed and the lights have normal brightness.

If you know how to use a voltmeter, you can connect the leads across the battery terminals.  Start the engine and observe the voltmeter reading.  It should immediately read about 14.5 volts or higher. If the reading does not change or you do not see a rise in voltage of one volt or less you will need additional diagnosis by a qualified auto electrician.  It would be advisable to get your auto tune up very soon.

Your alternator is a rugged electrical device in your car. It can withstand excessive heat and heavy electrical loads. But, a sudden voltage overload as in the case when someone tries to use jumper cables to power up a dead battery by crossing the connections, can damage your alternator in a hurry.

In addition, while your alternator rotates, it produces alternating current (AC) through an electronics circuit built inside it forming a “diode trio” that converts this current into direct current (DC) to power all the electrical and electronic devices in the car.

When one or more of these diodes fail, the output current is reduced.  While it may be producing some current it will not be enough to charge your battery fully—especially at slower speeds like when your car is idling.

If you suspect any of these problems it is best to seek the advice of a qualified auto electrician. They have most of the testing equipment for these kinds of problems and it is best to get the additional diagnosis done early to avoid damaging other sensitive components in your car.

If your alternator is found to be defective, it could be repaired but that takes too much time and would cost a lot. The better way to approach this is to buy a rebuilt one from a reputable auto store and get a rebate for the old one. Besides, most of the auto parts stores give a lifetime warranty so as long as you own the car, you can get a replacement if the alternator becomes defective for any reason.

NOTE:  (1) If you want to change the alternator yourself, be sure to disconnect the positive (+) red cable from the battery terminal before you proceed.  This is a precautionary step to avoid short circuiting any components and or starting a fire.

NOTE (2) it would be wise to inspect the drive belts at this time and replace them if they are cracked, glazed, oil soaked and show other signs of wear. Be sure to adjust the belts tension to the manufacturer’s specifications. Too much tension can ruin the bearings in the alternator and if the belts are too loose they may cause a fire as the belts slip while the engine is running.  The belts life will be shortened as well.

When you take these steps to get an auto tune up you will prolong the life of your car that will continue to give you many years of reliable service.