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Followed the guide on installing a HE280 hot end on a Rostock Max v2 however, when I first turned it on before installing the firmware, the hot end randomly heated up to somewhere around 200 C. While I thought this was odd, the heater turned off after reaching around 200 C and so I continued with installing the firmware and calibration. However, whenever I attempt to heat the hot end up in any way, the temperature doesn't change and the screen will throw a double "def" error on the temperature readings with the message "heater decoupled" a few seconds after the command is sent. At idle the thermistors both read around 25 C so I know the def error isn't related to them being too cold. I am also able to heat the bed up independently of the hot end without issue.

Solution: As one of the commenters suggested below, the issue was a blown fuse on the HE280 hot end. I replaced the fuse and it is working fine. I still do not know what caused the hot end to randomly heat up and blow the fuse when I first turned it on but it hasn't happened again.

I bet you blew the thermal fuse and will need to replace it.

g.

geneb wrote:I bet you blew the thermal fuse and will need to replace it.

g.

Scratch what I wrote earlier

You are right the Thermal Safety Fuse on the hot end is busted. I assume it happened when the hot end randomly heated up when I first powered on the machine. I guess the question now is why that happened.

You probably had a short somewhere. I've never heard of an actual instance of uncommanded heating ever happening on a RAMBo before.

g.

Would a short somewhere on the PCB of the HE280 cause this? All the soldering i did on it looked good but i am not the worlds greatest with a soldering iron. I'm trying to find the problem before i blow another fuse.

Also would there be any issue with using a little hotter fuse there such as a 120 C fuse rather than the 98 C? I ask mostly because i can get cheaper fuses and faster shipping from amazon but the lowest temp i can find is 120 C.

Don't change the fuse type. You may simply have it wired incorrectly - make sure the whip connector wiring follows the diagram in the docs.

g.

Ordered several more fuses in case I blow another one. Will update this post when they arrive. Thanks for your help

If you tightened the washer down to hard or with the weak little arms outside of the track you could have caused a short like I did where the thermistor wire was touching the hot end.

Side note, you can solder up a car fuse to your blown fuse. That's what I did while waiting the 2 weeks for a replacement to come from China.