The battery in a 2005 Ford Mustang is located in the back left corner of the engine bay, between the passenger side strut tower and the firewall. This battery is a top-post style battery. It contains two terminals, one positive and one negative. The battery leads slide over the terminals and are secured with a 10 mm metric steel bolt. Replacement batteries are available from auto parts stores and certified Ford dealerships.
Turn the ignition to the "Off" position, shift the Mustang's transmission into park (if you have an automatic transmission) or first gear (for manual transmission) and open the hood.
Loosen the 10 mm bolts on the positive and negative battery leads using a 10 mm box end wrench. Remove the leads from each terminal using a twisting/pulling motion. Remove any corrosion present on the battery leads using a wire brush.
Remove the 13 mm bolt from the battery hold-down wedge on the front of the battery tray using a 13 mm socket and a 3/8-inch ratchet. Remove the battery hold-down wedge. Carefully lift the battery up and out of the engine bay using two hands.
Place the new battery in the battery in the battery tray. Replace the battery hold-down and reinstall the battery hold-down bolt. Reinstall the battery leads.
Start the engine and verify that the battery operates properly.
