The answer to 'carbon monoxide detector not working' is that there are several common causes, including a dead or disconnected battery, a sensor failure, or a wiring issue. Symptoms may include the detector not lighting up, chirping, or responding when tested.
To troubleshoot, first check the battery and replace it if needed. If the battery is fine, the detector may need to be replaced if the sensor has failed. Wiring issues are less common but can also cause the detector to stop working properly. In most cases, replacing the detector is the best solution, as they have a limited lifespan of 5-7 years. If you're unsure of the cause or don't feel comfortable making repairs, it's best to call a licensed electrician to diagnose and fix the issue.