When your smoke alarm continues to chirp every few minutes even after replacing the battery, it might be time to replace the entire unit. The Firex FX1218 smoke alarm is a combination smoke and carbon monoxide alarm. This alarm is wired into your home electrical system with a battery backup. The alarm is designed to last for 10 years. Replacing a Firex FX1218 smoke alarm is fairly simple and replacement units are available at home improvement centers.
Remove Faulty Unit
Slide the battery compartment away from the Firex FX1218 smoke alarm with your finger just like you replace the batteries. Pull the 9-volt battery out of the alarm.
Find the plastic pin in the side of the main body. The pin locks the body onto the mounting plate. Pull the pin out with a pair of needle nose pliers.
Turn the body of the smoke alarm counterclockwise to unlock the tabs from the base. Gently lower the body and pull the wire connector plug away from the unit with your fingers.
Remove the screws securing the mounting plate to the junction box with a Phillips-head screwdriver. Lower the mounting plate and thread the connector plug carefully through the hole in the center of the mounting plate.
Install New Unit
Position the new Firex FX1218 mounting plate to the junction box. Feed the connector plug through the center of the mounting plate. Secure the mounting plate with the retaining screws.
Remove the tape from the top of the battery compartment door with your finger. Slide the battery compartment door open with your thumb. Insert a new 9-volt battery into the compartment and slide the door shut until it locks.
Plug the ceiling wire connector into the plug on the top of the smoke detector body. The connector will only fit one way. Remove the small round plastic pin from the top of the smoke detector with a pair of needle nose pliers.
Position the smoke detector over the mounting plate and twist the body clockwise to lock it into place. Insert the pin through the round hole on the side of the smoke detector body.