UM2 Temp sensor reading 40c too high

[mattkaz 0]

My nozzle seems to have gained an extra 40c over night. When I turn my UM2 on the Nozzle temp is reading 82c at ambient room temp and the bed is at 20c. Any easy pre-Christmas Fix's. I have done a factory reset an re-installed the latest firmware but it still thinks its running hot.

 

[mattkaz 0]

update im tired. its about 60c out not 40

 

[illuminarti 18]

Obviously something's not quite right there. I'd start by checking the wiring. Pull the mesh back on the head, and make sure the wires are in good shape, and all the connectors properly affixed. You might also take the cover off the electronics underneath, and check that the temp sensor wires are properly affixed there too. Note that there's one wire pair that runs from the electronics board to the head that isn't connected to anything - that's for the second extruder when available.

 

[mattkaz 0]

Thanks illuminarti, This morning I turned her on and its running a temp 105c maybe its got the flu! I will probably have to wait a day or two to strip it down. The top end looks ok though.

 

[gr5 2,210]

The way the thermocouple works - it's a very sensitive thing in that the arduino doesn't have the capability to measure it so there is a tiny circuit board on the head of the UM that measures the temperature and converts it to a voltage between 0 and 5V where 0V=0C and 5V=500C. So measure that voltage on the print head. The most likely thing that is broken is that board or the thermocouple itself (although the thermocouple is pretty damn simple!) or the wiring between the two. You can test this by measuring the voltage coming off the board. At room (20C) it should be around 200mv.

If it is correctly at 200mv (and not 1050mv) then the problem is not there and is in the wiring or in the UM PCB. But I strongly suspect the problem is in the head area and will be reading around 1000mv (1volt) instead of around 200mv at room temp.

 

[mattkaz 0]

Thanks gr5 i tipped the um2 on its side to how easy things are to get to but thought the wiser at this time of year. Turned it back up right and things are reading as they should be for now at least. I will have a proper look in a day or three as there must be something loose somewhere

[gr5 2,210]

You want to remove the large of the 2 covers down there and there are only 2 screws holding it on.

Everything is labelled. If you are lucky the cable in question is half disconnected already and obvious.

More likely the problem is in the head - you could slide up that black weave/web netting stuff and there are connectors in there. Maybe the temperature one is loose.