Hotend no temp. Heater is working


I have a Lulzbot TAZ3
Recently I have been doing some maintenance. Now after putting things back together I cannot get the hotend to heat up.
I’ve tested my heat resistor, and it gives a normal resistance @room temp (around 5 oHm)
The bed is heating up normally

Next, I’ve traced cables all the way down to the RAMBo board, and nothings seems fried at the first sight. What would be the best way to test that Mosfet outputs?

And last, please feel free to give random proposals and solutions for what else could be wrong :slight_smile:


What’s the resistance of the thermistor (orange wire pair leading to the hot end)? Does the hot end show the ambient temperature? Do your motors on the X/Y/Z axis move? The board has a fuse for the logic and for the hot end/motors.

Thank you Orias,

The resistance of the thermistor is about 120k.
The hotend shows the ambient temperature fine.
X/Y/Z motors are moving and working as they should.


If the motors are working and the printer powers on it’s not the fuses. The printer shows the ambient temp on the hot end, and your heater has a resistance of ~4.7ohms, the problem lies in the wiring or the connectors somewhere (or more rarely the mosfet of the board for the extruder heater- test for voltage from that output). If you disconnected the hot end from the printer while powered it can damage things, but you should be able to detect something from that connector, voltage wise when heating (say at 50c)


Thanks Orias. I’ve managed to solve the problem. The heater resistor wires needed to be stripped again, at the end coming to the RAMBo. Everything is replaced and back to normal.

Only thing is that I didn’t guide them through the plastic guide hose and to the back of the electric box. It’s rather tricky and I probably need to disassemble a lot of stuff in order to retrace the steps. So image below :slight_smile:

Now back to work. Hopefully printing a new longer mount and x carriage for stock Hexagon I’d got from MakerFarm