Q&A for How to Change an Alternator

It's usually a long ratchet or "breaker bar" used to loosen the bolt on the belt tensioner so that the serpentine belt becomes loose.

If you aren't sure how to diagnose this problem yourself, you can take your car to the shop and have them check your alternator (even if you do the repairs yourself).

Changing the alternator on most cars is generally the same. Find the alternator (has to be connected to the serpentine belt), and then look up steps to replace it. The main difference in cars is where the alternator is and how it's mounted.

Start out by replacing it. You might also want to test your battery to see if it still has juice since the alternator, which is supposed to charge it, failed. Also buy a new wiring harness to make sure maximum power is going throughout your car.

A set of sockets or spanners, and a lever to hold pressure on it to keep the belt tight when installing the new one.

No, it is best to remove battery cables and clean the terminals while it is off.

Yes, they often will.

If your alternator is broken, it may have drained your battery, but that doesn't necessarily mean the battery is bad. If it's been completely drained repeatedly, however, it may need to be replaced. Pull the battery from the car and take it to your nearest auto parts store to be tested - they can determine if the battery can still hold a charge.

Your battery is supposed to be at about 12 to 14 volts, if your alternator works that is where it will sit, maybe a little higher. You can plug a sensor onto the alternator and ground it off away from battery, then read it.

The inside of the alternator spins along with the pulley. Knocking sounds may mean there's something broken inside the alternator that's clicking as it's struck by the spinning assembly. You should have your alternator tested and it may need to be replaced.

The tools you'll need tend to be specific to the year, make and model of your vehicle - but some common tools are a socket wrench, standard or metric sockets (standard for American made vehicles, metric for foreign), a breaker bar, and a pry bar or large screw driver.

You should make sure the battery has a good charge so it can start, but it won't damage the alternator if it's a little low.

You need a long (heavy) flat-blade screwdriver, an adjustable wrench, a box or open wrench - or two, depending on the size of the nut to be loosened.

You most likely knocked the timing chain off just a bit, or the alternator you put on has a higher voltage output than the original.

That sounds like there's an issue with the alternator, but to be sure, you can remove it from the vehicle and take it to most auto parts stores for testing. If the alternator tests as fine, there may be an issue with the main power cable running from the alternator to the batter, or an issue with the battery's ground cable.

You need a new battery whenever it is defective, not just because the alternator is.

Imagine a stone hedge of magnets with a big coil of copper wires in the center.

Usually, it's just a long, metal bar with the wrench socket at the end that fits onto the belt tensioner.

Every car has a serpentine belt regardless of year or manufacturer, it is necessary to run the car.

Take your car to an automotive store and ask to check your alternator. If you don't want to do that, some signs are your headlights dimming when you put the a/c on, your car shakes when the a/c gets turned on, or your battery drains very low. An alternator powers everything in a car when it's turned on and running, the battery powers stuff when you only have the car set to run.

It depends on the mechanic you go to and whether or not they will try to scam you, but I wouldn't recommend paying more than $50.

Yes. Without loosening the belt tension, it'll be almost impossible to take out the belt from the alternator without breaking the belt. But you could honestly just use a ratchet that fits your tensioner and add a pole to the end to give you more leverage.

While the engine is running, disconnect one of the battery cables from the battery. If the engine instantly shuts off, you need to replace the alternator.

Positive (+) cables generally are red. Negative (-) cables usually are black. Battery terminals have a + or - sign on them.