How Your Car Alternator Works.by "batteriesontheweb"Eric Roberts

Eric Roberts 10-06-2011
Many of our customers have experienced problems with their car not starting, especially on cold winter mornings. The fault normally lies with a dead battery and once changed the problem is solved. Some motorists though suffer the unwelcome experience of the car not starting again a few mornings later. The irate car owner usually calls us shouting expletives about” how rubbish “our batteries are. We calm them down and recover their vehicle back to the garage where we can test the charging system.
The first step we take is to check the alternator charging voltage, we use a hand held portable tester for this job. We then measure the voltage of the battery with a voltmeter setting with the engine running. It should give a reading of between 13.5 and 14.5 volts. If the reading is below these voltage figures we can suspect that the alternator is at fault and will need replacing.
The alternator gets its name from the fact that it generates “alternating” current known as (AC). Batteries can only use direct current (DC), so the current from the alternator is transferred from AC to DC through what are called “diodes”. Your alternator is able to give out a high voltage when the car is idling. Your alternator is really three alternators in one. The three sections generate their own voltage out of step with the other two parts.
Therefore in one revolution the alternator puts out three separate voltages. Each three sections of the alternator has its own windings and diodes, either of these components can fail in service one part at a time, but the alternator can still give out a charge into the battery, if one part fails the other parts may still function, this may enable the alternator to carry on in a limited way for a long period before finally failing.
The failing alternator is usually found out in freezing conditions in the middle of winter when your heater/wipers/lights are needed at full pelt on a cold winters morning. Hope this gives my customers some insight to the workings of your cars alternator.Car batteries are available from www.batteriesontheweb.co.uk with a next day delivery through out the UK mainland