Heat bed not workin...
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Heat bed not working? (Solution to my issue)  

Active Member

Ok chaps, 

I see a lot of posts about heat bed issues regarding temp. 😆 

Let me set the scene.
My workshop in November has an ambient temp of around 12-15 degrees and i believe this to be the reason for the issue i have?! 🧐 

I had recently started up a print however the heat bed temp started to drop around 90% of the way there and the system just hung until i cancelled it to investigate. 

I tried it again and noticed that there was no head coming from the plate however the sensor was still working as i was able to apply external heat to the plate to test the sensor.

After a relatively sparse investigation i managed to narrow down my issue to the thermal fuse imbedded in the bed.
obviously no indication that it had blown however after a continuity test it became apparent that this was the issue. 

I have just ordered a new fuse to replace it.

There are no posts (that i have found) to show the tear down of the bed that led me to find this issue so i will try and post them once the fuse arrives and i am ready to put my hands on it again.

Although i dont condone anyone fixing there printer without first getting expert help or seeking a repair from CEL themselves, especially if still under warranty, However sometimes life calls you up and you have to solve things yourself. 

So my question is... Do you think that the cold temp in my workshop meant there was more strain on the heating side of things that it was over compensating? 😨 

Posted : 11th November 2020 3:21 pm
Former USA Robox Support Moderator

No, the fuse blew because of one of two things:

1. The thermal paste dried out and was not replaced. This lead to a loss of consistent thermistor contact and the bed temperature was hotter than the thermistor read, so the bed overheated.

2. The bed thermistor was not seated properly and the bed overheated.

I tend to recommend replacing the thermal paste every year. 

The thermal fuse is triggered only by temperature, not by load.

Make sure that it is the fuse and not the bed power wire. If the bed power wire has broken, which will give the same indication as a blown fuse, it can short the mainboard and destroy it. 

Posted : 12th November 2020 2:18 am

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