In your vehicle's charging system, the battery stores the power, and the alternator creates it. Without one, the other can't do its job, and the whole system fails. Changing the alternator on your Chevrolet Avalanche is a fairly easy task since the alternator is mounted high in the engine and is designed to be easily removed. But there are some slight complications in the process that may take an inexperienced mechanic a bit more time. In this case, the project vehicle is a 2003 Chevrolet Avalanche, but the process is similar for other vehicles as well.
Pop the hood and disconnect the positive terminal from the battery using the open-end wrench set.
Place a socket on the end of the breaker bar and place that onto the belt tensioner. This is an angled wheel that pushes down on the belt and keeps it secure automatically. Pull the bar to release tension on the belt then slip it off of the alternator. When reinstalling the belt later, there is a diagram on the core support in case you get lost.
Disconnect the positive battery terminal from the back of the alternator using the 3/8-inch ratchet and socket. Unplug the harness from the back of the alternator at the same time.
Unbolt the alternator from the mounts on the engine and lift it out of the engine bay.
Install the replacement alternator using the factory hardware and the 3/8-inch ratchet and socket. Make sure to plug in the harness using your hands and the battery connection using the open-end wrench set.
Pull the tensioner back with the breaker bar and place the belt back over the alternator pulley. Make sure that the belt is run correctly by looking at the belt chart on the core support before you release the tensioner.
Reinstall the positive battery terminal using the open-end wrench set.
