Preheat error

The Preheat error message occurs when there is a problem with the preheat process before your print starts. Therefore, there is something preventing the printer from heating up in proper time.

Make sure to distinguish between the Preheat error and the Bed preheat error. 

• Preheat error - a problem with preheating the hotend.
• Bed preheat error - a problem with preheating the heatbed.

Preheat error

1. Make sure that the ambient temperature is stable and there is nothing cooling the printer down, such as a nearby air-conditioning unit or an open window. 
2. Make sure the thermistor and heater are properly plugged into the electronics board. You can doublecheck that by following these guides: Mini RAMBo electronics wiring (MK2S, MK2.5, MK2.5S) or Einsy RAMBo electronics wiring (MK3/MK3S/MK3S+).
3. Check if the fuses are not blown.
4. Make sure that your hotend assembly is correct.
5. If the issue persists, then there is something wrong with your printer's thermistor or heater. In order to find out which one of these two is malfunctioning, perform the simple test described below.

Bed preheat error

1. Make sure that the ambient temperature is stable and there is cooling down the printer, such as a nearby air-conditioning unit or an open window.
2. Make sure the heatbed thermistor is properly seated under the heated bed and secured with the golden Kapton tape. If not, then simply put it back and make sure that the thermistor cable has some space for movement.
3. Make sure that the thermistor and heatbed are correctly plugged into the electronics board. You can doublecheck that by following these guides: Mini RAMBo electronics wiring (MK2S, MK2.5, MK2.5S) or Einsy RAMBo electronics wiring (MK3/MK3S/MK3S+). 
4.  Check if the fuses are not blown.
5. If the issue persists, there is something wrong with your printer's thermistor or heater. In order to find out which one of these two is malfunctioning, perform the simple test described below.

It is not very common, but there is a chance that only the thermistor is defective. You can check it using the following test: 

1. Use a hairdryer to blow hot air at the heatbed or hotend.
2. In the meantime, check if there is any temperature change on the LCD screen.
3. If there is a positive temperature change it means that the heatbed or hotend thermistor is working. Which means there is something wrong with the heater or heatbed. In both cases contact our support and they will provide assistance.
4. If there is no change at all, the hotend or heatbed thermistor is defective.