How to Troubleshoot Smoke Detectors That Are Hardwired

Remove the fuse or trip the circuit breaker in the fuse box that allows electricity to the section of the house where the smoke detector is located. Stand a ladder against the wall where the smoke detector is. Remove the screws around the collar or base (depending upon the make) of the detector with a Phillips jeweler's screwdriver. Remove the detector from the wall.

Loosen the screws on the junction box that the wires connected to the detector are screwed around with the screwdriver. Unwind the wires and scrape their exposed ends with the blade of a utility knife. Wind the exposed ends of the wires around the screws they were just unwound from. Screw in the screws. Place the detector back over the junction box and reattach the screws. Place the fuse back in or trip the circuit breaker in the fuse box to restore power to the detector.

Verify that the red LED on the front of the smoke detector is flashing every minute, rather than once every few seconds, which indicates that the battery backup supply inside the detector is running low on power. Remove the front of the detector by rotating the front counterclockwise or by removing the screws surrounding the collar with a Phillips jeweler's screwdriver (depending upon the make of the detector). Pull the battery clip off the contacts on the battery. Pull the battery out of the battery compartment and discard it properly.

Insert a replacement battery into the battery compartment and attach the battery clip to the contacts. Place the front of the detector back on by either rotating it clockwise or reattaching the screws.

Press the "Test" button on the side of the smoke detector and hold it in for five seconds before releasing it. If the horn (alarm) does not sound, the electronic circuit board in the detector may be damaged and inoperable. Verify this test at least two more times before purchasing a replacement smoke detector to take the place of the one that is defective.

Remove the front cover from the smoke detector -- the cover twists off counterclockwise or may have screws to be loosened first with a Phillips jeweler's screwdriver. Wipe out the inside of the cover with a soft cloth. Blow out the inside of the cover with a burst of compressed air. Locate the sensor plate on the smoke detector -- the plate is a dull metal color, unlike the rest of the circuit board it is lying on. Blow off the sensor plate with a burst of compressed air. Rub the sensor plate with a cotton swab moistened in lens cleaning solution to remove dirt, grime and other contaminants that have gotten deposited on the surface. Wipe the sensor plate clean with an edge of the cloth. Blow off the sensor plate with a burst of compressed air. Place the front cover back on the smoke detector by either twisting it clockwise or reattaching the screws.