A multi-function sight port door includes a sensor mount attached at an aperture within the sight port door. A sensor is mounted to the sensor mount and configured to monitor the interior of a heater that the multi-function sight port door is mounted to. The multi-function sight port door is also configured to open to allow visual inspection of the interior of the heater while the sensor is mounted thereto. The multi-function sight port may be configured to allow for one or more of X-axis, Y-axis, Z-axis, tilt, roll, and yaw positioning of the sensor as mounted to the sight port door. The sensor may be a temperature sensor, pressure sensor, flame scanner, gas analyzer, optical-based sensor, thermal imager, thermal camera, or laser-based analyzer.