Friday, September 7, 2012

Finding Alternator Faults

Finding Alternator Faults


Checking the alternator to make sure it is charging properly will save a lot problems in the future.The light on the dashboard known as the battery light will let you know if the battery is being charged or not.If your car is fitted with an alternator and not a dynamo, then this light should work for most cars, in exactly the same way.Once you turn the ignition key to the "ignition on" position, the ignition light should come on.Once the engine has started running the light should go out fully or at least as soon as you get above an idling speed.If the light does not come on at all before the idle speed or comes on after the idle speed, then there is a fault in the charging system.If the problem is the light does not come on at all and the wire is connected, the most likely cause is the bulb may have blown in the dashboard.The bulb is normally behind the instrument cluster so may not be that easy to get to.If the ignition light comes on after the idling speed, then there could be more than one problem.The first thing to establish is if the battery itself is suitable for charging, for example, if the battery is so dead that it cannot take the charge this could be the reason.The gravity of the electrodes in each cell will have to be checked with a battery hydrometer.This is particularly important for batteries that have been standing around for a long time.Then check the battery is connected properly with good connections and a smear of Vaseline to prevent any corrosion.If the battery is suitable for charging and connected properly, then check the tension of the drive belt to make sure it is not slipping.If that looks fine, then test the alternator is working by putting a multimeter across the battery whilst a friend revs the engine check to see if the volts raise from 12 volts to around 14volts.If the volts do not rise, you will have to investigate further.Most connections to the alternator are done via a multi-plug.Check first to make sure the plug has not come loose.If it has, push it back in and take the reading again.If the volts are still not rising, then remove the multi-plug and with the multimeter put the negative wire of the multimeter to the earth of the car and then test each connection of the multi-plug with the positive probe.If you see 12-14 volts on each connector, then the alternator will be deemed to be at fault.Normally at that stage an auto electrician should be able to tell you if it is just new brushes that are needed or a replacement alternator.

Finding Alternator Faults



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