The alternator keeps the battery in your Pontiac going, constantly recharging it as you drive. The battery will quickly drain if the alternator is bad, so it must be replaced in that case. The alternator is mounted in the engine and naturally connected to the battery in all models, but other components could be in its way depending on the type of Pontiac you own. This will determine how difficult such a replacement will be.
Open the hood and disconnect the negative cable from the car battery.
Remove the drive belt by rotating the belt tensioner with a wrench to relieve the tension, slipping the belt off while applying pressure from the wrench. Depending on the model, other components might need removal, like parts of the air cleaner (Grand Am and G6), the fuel injector sight shield (Bonneville) or the coolant recovery reservoir (Grand Prix).
Disconnect any wire clamps that are on the clip at the alternator's end frame, then remove the rubber clamp and nut. These extra fasteners are not on all Pontiac models. Disconnect the electrical connector for the alternator. Remove the alternator by disconnecting its bolts.
Mount the alternator in place on the engine and tighten the bolts to the specified torque for your model. Connect the electrical connector to the new alternator along with any other clamps that held the old alternator.
Replace the drive belt by pushing the tensioner upward and slipping the belt back on it and the pulleys in the same way it was originally wrapped, then tighten the tensioner to the torque required for your vehicle. Replace any other components that were removed and reconnect the battery cable.
