ER03 - Heater error

The heater error can appear when the sensor doesn’t register a steady (increase in) temperature. To prevent overheating of the nozzle, the printer will turn off heating.

There are a few things that could cause this error message:

Check the print head

Take a look at the back of the print head. Ensure that both the heater and the sensor are still secure in the heater block. If one of the wires (or both) is loose, the temperature cannot be accurately measured.


Tip: As seen from the back of the print head - Left is the heater, right is the sensor.

If one of the wires is disconnected, reinsert it into the heater block and tighten the screw to secure it. If one of the wires looks damaged, it must be replaced.

The heater error can also appear if an incompatible combination of parts is installed. The hot end parts of the Ultimaker 2 and Ultimaker 2+ series are different.

Ultimaker 2 The Ultimaker 2 has a small heater block with integrated nozzle (part 1301), a PT100B sensor (part 2225), and a 25W heater (part 1268).
Ultimaker 2+ The Ultimaker 2+ has a larger heater block (part 225874 / 1471), a glass fiber PT100 sensor (part 2288), and a 35W heater (part 2283).

Although the Ultimaker 2+ parts are compatible with the Ultimaker 2, they should only be installed as a set, not individually. The different properties of these parts would lead to issues with temperature regulation.

Tip: For the Ultimaker 2, consider the Extrusion Upgrade Kit for improved reliability and enhanced flexibility.

Check the nozzle

The fan bracket contains a hole for the nozzle at the bottom. If the nozzle touches the side of this hole, the heat will spread throughout the fan bracket. This makes it hard for the printer to maintain the correct temperature.

Closely check the bottom of the print head. Ensure the nozzle is in the center of the hole and not touching the sides at all. If it is, you can correct the position of the fan bracket.


Loosen (but do not remove) the two bolts at each side of the fan bracket. Adjust the fan bracket's position so that the nozzle is in the center of the hole. Then, retighten all four of the bolts.


Tip: You can also use a 3D printed nozzle alignment tool. Place this around the nozzle before retightening the As seen from the back of the print head - Left is the heater, right is the sensor.

Fan settings

When printing a model with a big flat surface, the airflow from the side fans could bounce off the model against the print head. This cools down the nozzle. In this case, it can help to decrease the fan speed.

In Ultimaker Cura, go to the Custom mode for the print settings and go to the Cooling section. Choose a lower fan speed and reslice your model.

Need further support?

If you require further assistance with troubleshooting, or when you need replacement parts to resolve the issue, contact support or your local reseller.

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