Buying an Alternator – What you need to know

alternator sample

Used alternator

When you are looking to buy a Alternator to replace your old one it is important to match up the part numbers to be sure it’s the correct one for your car. Getting it right the first time – You do not want to purchase the wrong one and then have to go though the process of finding the correct one all over again.

At Your Car Spares Ltd  – What we test and look for!!!!

Ever part is different so we need to look out for different things for different parts. With Alternators  we look out for the general condition (not to old and worn). We also test the Alternator to see what voltage it’s putting out into the battery we mark this information on a label which we attach to the alternator. Alternators from cars that don’t run because of engine or electrical problems can’t be tested so we make a decission on weather to keep it or not. This depends on the condition of the alternator and the reason why the car is a end of life vehicle! Cars are not end of life because of an Alternator problem so it is very very unlikely that a end of life car we are dismantling because of engine or electric problems had a problem with the Alternator!!!

alternator parts number

How to find the alternator parts number.

Where to find the Part Number

Where to find the part number depends on the make and model of the Alternator. On most if not all Alernators the part number and  Amps are found on a label on the side or end of the Alernator.

In the following images we show you where to find the part number and the amount of Amps your car requires so you can cross reference it with your parts number and Amps to be sure it’s the correct Alternator for your Car.

It is important to purchase a Alternator with the same Amps and not one with less. If you purchase  one with less Amps it will not not charge your battery fast enough so you can use all the cars electrics when required.


How a Alternator works ?

Your engine runs on fuel, air and a spark ignites the fuel. Electricity is needed to generate a spark, a cars battery supplies the electricity needed, but only enough for a few miles and more is needed for the journy to carry on. That is where the alternator comes in. The reason for the alternator is to continually charges the battery so it never goes flat. A car Alternator has an output of between 13.5 to 14.8 volts keeping your 12 volts car battery 100% charged so all the car’s electrics can be used when needed.

The alternator has four main components: The Stator, Rotor, Diode and a voltage regulator. When  your alternator belt spins the alternator pulley, inside the alternator is the Rotor (which is basically a magnet or group of magnets) which spins very fast inside a ball of copper wires which is called  the stator. The Rotor spinning inside the stator produces electricity. Then Diode changes the electricity current from AC to DC which your battery uses. The final step in the chain is the voltage regulator, it’s job is to shut off the flow of current to your battery if the voltage gets to much and stops your battery from overcharging and therefore getting cooked.

Alternator spare

One of the alternators available

Testing a Car Battery

There is only one way to know if your battery is GOOD or BAD and that is to test it. There are many places that will test your battery for free. If you are unable to drive your car to have the battery tested remove the battery and just take the battery to be tested.

How Low is your Is the Car Battery?

The key test is to check to see if the voltage of the battery is more than seventy per cent charged. In effect, it is shows as being below 12.45 volts then you should recharged such as by using going for a twenty minute or so drive, or alternatively, by using a mobile charger unit.

Why You Need a Good Battery for Reliable Cold Weather Starting

A good battery is essential for reliable starting, especially during cold weather because cold weather increases the cranking load on the battery. Oil gets thicker at low temperatures so it takes more amps to crank a cold engine when you try to start it. At 0 degrees F, the number of cranking amps it takes to start a cold engine may increase as much as 2X. At minus 15 degrees below zero F. , it can take 3X or more amps to crank the engine depending on the viscosity of the oil in the crankcase. The thicker the oil, the harder is it to crank the engine. At the same time, cold temperatures also sap the battery’s ability to supply amps. At 0 degrees F, most batteries can only deliver about 65% of their normal cranking amps. At -20 degrees, battery power is cut in half!

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