Heatbed is not heating up properly

Updated 2 months ago ​by Tomáš Chvalina

In this article, we will go over couple of things which might cause your Heatbed not to heat up properly. 

Heatbed does not heat up

If your Heatbed does not heat up at all, most likely there is something wrong with the assembly or the Heated bed is permanently damaged.

Check following:

  1. Visually check if your Heated bed is not badly damaged or does not have exposed traces.

  2. Check if your Heated bed thermistor is properly attached under the Golden Kapton tape.

    If you notice the thermistor is hanging freely, unattached to the bed, undo the 6 bolts holding the bed to the Y carriage and re-secure the thermistor.

  3. Loosen Heated bed connectors on the miniRAMBO board. Simply open the miniRAMBO box and un-plug and re-plug the connector.                                                                                                                                               
If none of the above helped. Please follow the instructions bellow for less common cases.

Heater or Thermistor does not work

It is not very common, but there is a chance that extensive printing damaged your heater or thermistor. 

The most effective and the easiest solution is to take a hair dryer and blow hot air at the Heatbed. During this process just check if there is any temperature change on the LCD. If there is a change it means that your thermistor is working, which means that the heater is damaged. If there is no change at all, your thermistor is defective. 

To see whether the surface is heating properly around the whole surface, we suggest wiping down the heat bed surface with Isopropyl alcohol (IPA) cold and then preheating. The alcohol will evaporate when heated, exposing areas that are not heating at all. 

Loss of power/ Slow preheat process

Remove the printed cover at the back left of the heated bed and check following.

  1. Damaged Heated bed cables at any spot
  2. PSU cables properly attached to the miniRAMBO board and not damaged at any spot 
  3. The blue fuse (15A) on the Rambo board is still intact: Blown Fuse (miniRAMBO)
Usually the cables around the Zip-ties can be damaged as these cables are under heavy work load.
Please try the following if you have access to a multimeter to get some data to see if the Heatbed components are out of spec or potentially problematic. If you are unfamiliar with how to use a multimeter, here is a good tutorial you can look into.
Measuring resistance:
  • The resistance of the Heatbed thermistor should be approximately 100K  ohm  at room temperature (same goes for the thermistor on the hot end if you are curious!)

  • The resistance of the heated bed should be 1 ohm (don't worry if the resistance oscillates around 1 ohm)

Measuring voltages:
  • The voltage coming to the heated bed should be ~12V
  • The voltage coming from the PSU to the Rambo Mini should also be ~12V.

If the issue persists after trying all the above, contact our support team at info@prusa3d.com. Be sure to include the fact that you've tried the above steps and any measurements you may have obtained.

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