How to Change an Alternator?

How to Change an Alternator

The vehicle’s alternator provides power to charge the battery and run the electronics. If your vehicle shows signs of reduced performance, such as You can have your alternator test free of charge at most auto parts stores. If it can’t generate enough electricity to charge your battery and keep your car running, it will need to be rebuilt or replaced. Read on for all the details on replacing an alternator.

What Tools are Needed to Replace an Alternator?

Before you get to work, you’ll want to gather all the necessary components. Choose a level, safe work area. In addition to a replacement alternator, you’ll need some tools:

  • Hand tools like ratchets, sockets, and wrenches
  • Belt tensioner tool
  • Gloves and safety gear
  • Battery tender or memory saver, if necessary
  • Jack, jack stands, and wheel chocks, if necessary

Automobile designs vary greatly from car to car. You may need something else, and many cars don’t need the last two items to get the job done, although some do. It all depends on how your make and model was made.

How to Change an Alternator

Safety is the top priority for all work on your vehicle. As you may need to jack up the vehicle, make sure it is parked on a surface suitable for the work. It should be evenly paved and level. When you’ve got all your gear ready, you can finally get started. Here’s how to change an alternator:

How to Change an Alternator

1. Disconnect the negative battery cable.

This step is crucial if you want to avoid a short and trust us you will do so. Before disconnecting the negative cable, consult a vehicle repair manual to determine whether or not a battery conditioner should be used to avoid drivability and/or module reprogramming problems. Make sure the ignition is also in the “OFF” position. Now disconnect and cover the negative (ground) terminal of the battery to avoid contact while working.

2. Disconnect the Wires

Now that the battery is out of the way, disconnect the wire or wires from the back of the alternator. This is usually a very simple process, but if you’re not sure where they’re going, label them when you lose them.

3. Inspect Related Components

While looking at the alternator, check the following related parts of the starting and charging system:

  • Drive Belt: This should be changed every 90,000 miles and while you’re replacing your alternator, a perfect time to replace this belt is when its time is almost up. Look for tears, frays and general wear and tear. A worn drive belt will generate noise and reduce alternator performance. Check and replace additional belts as needed.
  • Drive Belt Tensioner: If present, the belt tensioner can be checked when removing the drive belt. It should feel “smooth” without “sticking” or ” binding ” as it swings back and forth with the tensioner tool. The belt tensioner must not be extremely tight or loose. Also check the alignment of the drive belt and pulley(s). A worn pulley (idler) or tensioner will cause belt slippage, squeaking noises, uneven belt wear, and poor performance of the alternator and other drive belt accessories like the power steering pump.
  • Electrical Plug Pigtail Connector: Make sure alternator connection and wire harness are clean and intact. A loose terminal or a damaged pigtail connector can cause power and charging problems. Replace any damaged or worn components. Use a small amount of waterproof grease (dielectric grease) on the connector and alternator connector during installation.
  • Battery Terminal B+ Voltage Wire: The alternator 12-volt battery lead can become worn or damaged over time. If it looks “burned,” has a cracked or melted terminal end, has damaged or missing wire insulation, or feels “stiff,” the battery cable should be replaced. Otherwise, alternator performance will be reduced and may even cause an electrical fire.
  • Contamination on the Alternator like Oil, Grease, or Antifreeze: A little contamination of the outer surface is normal. However, if the alternator is covered (soaked) in engine oil or other liquids, the source of the contamination must be found and repaired. Contamination can shorten the life expectancy of the alternator and possibly void the manufacturer’s warranty.

4. Loosen and remove the serpentine belt.

Loosen the serpentine belt by springing back the belt tensioner with a belt tensioner tool. Pay close attention to how the belt connects to the other components, because when you’re done, you’ll need to re-route the belt around all of the engine’s pulleys. If possible, check the belt routing diagram for your vehicle.

Remove the belt and scan it for signs of wear such as tears or frays. Also check the belt tensioner to make sure its pulley still spins easily. If any of the components appear worn, replace them.

5. Loosen and remove the alternator.

Remove the alternator from the engine compartment. With the belt off the alternator pulley and the wires disconnected, the alternator should come out freely. You may have to wiggle the alternator around a few things to remove it. Watch as you unscrew the alternator from the engine bay to press in the new one.

Signs of a Bad Alternator

6. Compare the new alternator to the old one.

Before installing the new alternator, place it on a table next to the old one you just removed. Make sure the mounting holes and cable connectors are in the same place and that the two parts are the same size. Although you provided specific information when purchasing the alternator, this step is important to ensure you receive the correct part. If they don’t match, take the new alternator back to the auto parts store for the correct replacement.

7. Install the new alternator, making sure it fits and aligns with the bolt holes.

Carefully align the working alternator mounting holes and loosely install the mounting bolts and nuts. Make sure all bolt and/or nut threads have started and tighten evenly. For accessibility reasons, some vehicles require the electrical connections to be installed first before permanently tightening the alternator.

8. Reinstall the belt.

Either install the new belt or feed the old belt back through all the appropriate pulleys. If you’re not sure how to route the belt properly, use the photos you took earlier. You can also look for a diagram on the car’s body in the engine compartment to guide you. The belt must loop around each accessory it is intended to power in your specific vehicle.

Hold the tensioner loose with pressure on the ratchet. When the belt is properly seated in the various pulleys, slowly release the ratchet to allow the tensioner to re-tension the belt. If there is no diagram stuck in the engine bay, you may also be able to find the diagram in your vehicle’s owner’s manual. You may also find the diagram on the manufacturer’s website.

Apply tension to the alternator with a pry bar if necessary and tighten the bolts and the belt.

9. Reconnect the cable.

Connect the power cable and monitor harness. Reconnect the wire harness and replace the screw that secures the main power wire to the alternator in the same order that you removed them. They should be installed exactly as they were in the old alternator.

Reconnect the battery. With the new alternator in place, all you have to do is connect the negative cable to the battery. Make sure you tighten it tightly so it can’t come loose while riding.

How Long Does It Take to Change an Alternator?

Replacing an alternator will take a professional about two hours. However, that doesn’t mean your car will only be at the shop for two hours—there may be a wait before a mechanic can address your ride. It also takes even longer if the workshop has to get parts delivered. However, most stores in the US will charge you for a full day’s work.

If you decide to do the change yourself at home without much experience, it will take around 3-4 hours depending on the make and model of your vehicle. If you have no mechanical experience, please do not attempt to replace your alternator yourself; You can damage your car or injure yourself when working with electricity.

How Much Does It Cost to Replace an Alternator?

Alternators can average anywhere from $100 to $350 depending on make and model. Most vehicles will have an average cost between $350-400 for the total job of an alternator replacement if no other parts need to be replaced. If the serpentine belt is included in the process, add another $20 to $50 to your bill.

If you decide to use dealer parts and labor, expect the bill to climb well over $500 in many cases. Since the total cost depends on the vehicle, you can expect to pay anywhere from $350 to $900 for an alternator replacement.

How to Replace An Alternator?


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