At firealarm.com, we understand the importance of addressing issues with fire alarm equipment promptly. When troubleshooting the Notifier FSP-851 Low-Profile Intelligent Photoelectric Sensor, start by checking the power source to ensure it’s receiving adequate voltage. Next, examine the wiring connections to verify they are secure and properly terminated. Additionally, inspect the sensor for any visible damage or obstructions that may be affecting its functionality. If these initial steps do not resolve the issue, consult the device’s manual for further troubleshooting guidance or contact a certified technician for assistance. Remember to always prioritize safety when working with fire alarm systems.