How To Change The Alternator In Your Car

In order to get your car started and to keep it running, you need one very important part to be working: the alternator.  Once the car is started, the alternator continues to supply enough electricity to charge the car’s battery and keep all the electrical components in your car up and running. Without a fully functioning alternator, your car most likely will not start, or your car could completely stall out while you are driving. 


Failing Alternator Warning Signs:

  1. Check engine light is on
  2. Dim or flickering headlights, dashboard lights or even the dome lights 
    • (Expert tip: If the light or lights become brighter as your RPM’s pick up, it is most likely a faulty alternator and you should replace ASAP). 
  3. Strange noises coming from the belt slipping which causes lack of charge and a squealing noise.
  4. Power operated equipment within the car does not work such as windows, locks, power seats and radio. 
  5. Car stalling and or not starting. Due to the fact that the car battery and alternator work so closely together, the two can often share the same warning signs.  One way to decipher if you need a new battery or a new alternator will be if you jump start the car, and the car dies again while driving, the issue is most likely a malfunctioning alternator. 


Where Is The Alternator Located?

The alternator is usually located at the top of the engine towards the front of the vehicle. The alternator is usually round with ventilation slits, in which there is visible copper wiring. 

Alternator Location


How To Test a Car Alternator

To test your alternator, you will need to purchase a voltmeter.  Voltmeters are available at any automotive store.

  1. Check your battery by first turning off your car engine and opening the hood.  You will connect the red component of the voltmeter into the positive battery connection & the black component to the negative battery connection. Be very cautious that your skin does not touch the battery to avoid any burns. 
  2. When you read the voltmeter and it reads between 12.2- 12.6 volts or higher, the battery is supplying enough electricity to start the car. 
  3. Start your car and rev the engine to 2,000 RPM.  Your voltmeter should read between 13- 14.2 volts or higher.  If the voltmeter reads the same or lower as it did previous to revving the engine, your alternator needs to be replaced. 
Testing An Alternator


How to Remove Your Alternator

Once you’ve identified that your alternator needs to be replaced, it’s time to remove the old one. These are the steps you’ll need to follow:

  1. Locate the negative battery cable and disconnect it from the battery. The negative battery cable is indicated by a (-) sign, and you will need the correct socket wrench to loosen the bolt and disconnect the cable. 
  2. Locate the positive battery cable and disconnect it from the battery. The positive battery cable is indicated by a (+) sign, and you will need the correct socket wrench to loosen the bolt and disconnect the cable. 
  3. Remove the main power cord from the alternator by using an open-ended wrench to loosen the bolt. The main power cord can be identified as thick and connecting the alternator to the battery.  Once the bolt is unfastened remove the cord from its connection. 
  4. The last item you will have to disconnect is a control harness. Release the tab on the control harness and pull the two sides apart from one another. 
  5. Relieve the tension on the belt by inserting the square side of a breaker bar into the hole of an auto-tension pulley and rotate clockwise. 
  6. If your belt has a glossy appearance or has any cracks, your belt needs to be replaced as well. 
  7. Unbolt the alternator from the engine by rotating the bolts counter-clockwise. 
  8. Your alternator may need some slight wiggling in order to get it fully out of the engine bay, but it should come out relatively easy once the wiring and belt are removed. 
  9. Double check that you have purchased the correct alternator. You can do so by comparing the two side by side and making sure all the connection sizes are the same. 


How to Install an Alternator

Now that the old alternator is out, it’s time to install the new one so you can be back on the road! Start by placing the new alternator where you removed it, making sure that you are not trapping any wiring or connections. Then follow these instructions:

  1. Attach and tighten the mounting bolts by hand into the mounting bracket, tighten all the way if your car is equipped with an auto tension pulley for your belt.  If your car does not have an auto tension, do not tighten the bolts completely. 
  2. Place the belt back over the alternator pulley system. If you do not know the exact route of the belt, there should be a diagram located in the engine bay.  If there is not a diagram, check your owner’s manual. 
  3. Tighten the belt with a pry bar by carefully pushing the alternator away from the engine if your car is not equipped with an auto tension pulley. 
  4. Tighten all the remaining bolts with the appropriate socket and wrench until the bolts are completely installed. 
  5. Reconnect the control harness into the new alternator.  The plastic harness that holds are the wiring together will make a clear “click” sound when inserted correctly. 
  6. Locate the positive battery cable and connect it to the battery. The positive battery cable is indicated by a (+) sign, and you will need the correct socket wrench to tighten the bolt and connect the cable. 
  7. Locate the negative battery cable and connect it to the battery. The negative battery cable is indicated by a (-) sign, and you will need the correct socket wrench to tighten the bolt and connect the cable. 


Shop OEM Alternators and Accessories

There you have it - how to test, remove, and replace your old alternator. The alternator is one of the most important parts in your vehicle, so you want to make sure that the replacement you get is high quality. Only OEM alternators and accessories are built to fit your car perfectly, so you don’t have to worry about quality. Find parts you can trust here on our site!