The Fuse 1 monitors temperature changes inside the build chamber with an infrared (IR) sensor positioned in a compartment at the top of the printer. The sensor faces downward, pointing directly inside the Fuse 1's print enclosure. It is embedded in a grey cap with a green LED in the center that lights up if the sensor is correctly seated.

The IR sensor is located in a compartment at the top of the Fuse 1, above the touchscreen and next to the hopper. It may be difficult to reach, so consider keeping a step-stool nearby.

Examine the IR sensor for streaks, stains, dust, powder, or other contamination before every print to ensure success.

To check the IR sensor:

1. Open the IR sensor door in the compartment at the top of the printer.
2. Grip the IR sensor cap and pull. The IR sensor is held in place with magnets and comes out with little force.
3. Inspect the lens on the underside of the IR sensor cap:
   • If the lens is clean, reinstall the IR sensor.
   • If it looks contaminated, clean it with a polyester swab wetted with ethanol before returning it to its original position.

Inspect the O-ring at the base of the IR sensor shaft for damage or contamination.

If the IR sensor looks dirty or contaminated during inspection, wet a polyester swab with ethanol and use it to clean the lens.

To clean the IR sensor lens:

1. Check the IR sensor lens for dust, powder, or other contamination.
2. Wet the polyester swab with ethanol and wipe the lens.
3. Check the lens to ensure that there are no streaks and that the contamination has been fully removed.
4. Return the IR sensor cap to its original position once the lens is dry and clean.

The IR sensor is connected to its mount with magnets. Push in the cap until you feel a click and the LED turns green.

To reinstall the IR sensor:

1. Push the IR sensor cap into the mount. The LED turns green when it is fully connected.
2. Close the access door to the panel.