How to change an Alternator

When the time has arrived to change your alternator


It is not that difficult a job, and certainly one that most novice mechanic can do.

A good indication of a novice mechanic would be one that has purchased a ‘workshop manual‘ for their car and also owns a modest tool kit (socket set etc.)

Talking about tools ;
Before starting any job, always try and find out exactly what tools you will need to complete the job and make sure you have them to hand.  If you don’t, then go out and borrow or buy them BEFORE you get started.

I have started jobs on many occasions only to find out that I did not have the correct tools to complete the work.  That made me the ‘tool’, because I would have to put the car back together, go and buy the bit and then redo the work I had just done. Not clever, and most of the tools you buy can be used for other jobs.

Price up an alternator for your motor


engine bay showing position of alternator

Our ‘what is an alternator’ article already showed you where it is and how it works, so now we will show you how to change one.

Nearly all alternators are fitted to cars in the same way, so this article will give you general steps that should suit nearly every car.

If you want instructions that are specific to you car then you must get yourself a workshop manual specific to your car. They only cost £15-20 and will pay for themselves in no time at all.


How to replace alternator

1. Open your bonnet and disconnect the battery positive+ terminal.

2. Locate the alternator, and identify the top and bottom mounting brackets.

The top mounting bracket is normally the one that controls the tension on the alternator belt.  Remove this bolt and the alternator should move towards the engine and release the tension off the belt.

alternator brackets

3. Move the belt from around the alternator pulley and position it out of the way.

4. Now remove the lower pivot bolt, releasing the alternator from it’s position.

5. All that is remaining now is to disconnect the wiring that is attached.

alternator wiring

Here is another example ;

alternator wiring

Remember where the wires all fitted, mark them up if necessary.

6. Fitting the new alternator is a direct reversal of the steps you just did.

The last bolt to be fitted should be the one that controls the tension.

Position the bolt in place but do not tighten it.

Now pull the alternator away from the engine, thus applying tension to the belt and then tighten the bolt.

7. Check the tension on the belt, grab it with your fingers mid-way between 2 pulleys and more it forward and backward.

There should be no more than 1/4 to 1/2 inch of movement.

If there is more then loosen the bolt again and apply more tension.

You either need to get the assistance of someone else, or what I have done is get a large screwdriver or similar and use it
lever the alternator forward whilst re-tightening the bolt.

If the belt is not tight enough, it will slip sometimes resulting in a squealing noise but most importantly the alternator will not turn and will not recharge your batter.

8. Refit the wiring, refit the positive+ terminal to the battery.

9. Test your alternator by starting the car.

Price up an alternator for your motor

Here is one of many useful videos that we found ;

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