Solved Thermistors suddenly reading 0

So when I open up mattercontrol or any other controller program, I cannot get a reading from my thermistors, they just read 0 degrees.

It happened spontaneously about halfway through a 6 hour print, the printer just stopped printing, though MC showed that the print was still in progress. I shut everything down, and when I restarted everything, MC couldn't get a reading from either the bed thermistor or the extruder thermistor.

I know that a 0 reading is usually the result of a loose wire, but nothing appears to be loose, and that still wouldn't explain why BOTH the bed and extruder thermistors suddenly started reading 0.

Anyone have an idea what happened here? Currently the only thing my printer will do is go home.

Additional info:
-Im running a kickstarter PLA/ABS model with the heated bed
-I have an E3D V6 installed

 

Ill give the connections a sanity check when I get home. I did give the board connections a look last night, and everything appeared to be in order, so assuming my connections are all good, Im most likely looking at a RAMPS board failure then?


Thanks for the help!

 

Only time I've ever seen an arduino not read temp was when the thermistor pin wasn't properly soldered. I highly doubt this is the case and more than positive it's a loose/broken wire

 

Given that both thermistors started reading 0 at exactly the same time, that doesnt really make sense to me. Would both connectors really have come loose at the same time?

 

I've seen stranger behavior. Best way to know is to measure the resistance at the input terminal. Should be around 100k.

 

Alright, so Ive double sanity checked the connections, and everything is in order. Still no dice from mattercontrol or repetier-host on either thermistor.

Mike, where exactly should I be testing for resistance? Am I making sure my thermistors haven't gone bad, or am I checking the the pins on the board?

 

I would start with the wires right where they connect to the board and work my way back towards the thermistor. Resistance should be 100k.

 

So after testing, both thermistors are reading 0 ohms on my multimeter, does that mean they are actually dead?

 

most likely.

Try and measure at a point closer to the actual resistor (thermistor) to confirm.

 

Measured as close as humanly possible on both (On the extruder, directly measuring the thermistor). Needle on the multimeter doesn't even twitch.

Im happy because thats a pretty cheap and easy fix, but Im also a little concerned that they both crapped out at EXACTLY the same time. Should I be worried about that?

 

Most likely means a broken wire. Follow the wire and look for a break.

Also try and measure the resistance at various points starting near the thermistor to see if it's actually the thermistor.

 

Ive gotten pretty much as close to the extruder thermistor as I can (as you can see in the picture, lol). Its a little tougher on the bed since the only exposed wire is at the very end at the board connector itself, but that also reads 0 ohms.

edit:
Second picture is just to show that the multimeter is working.

 

Update: My multimeter hadnt been calibrated for resistance. After I calibrated it, both thermistors showed a slight "twitch" on the needle (bed twitching more than extruder), which means they are, at the very least, not totally dead. Im going to see if I can borrow a friends digital multimeter to get a more accurate resistance reading.

This now presents an issue, because the bed thermistor was giving a reading all the way at the end of the wire, where it connects into the board, yet still reads 0C when I start up mattercontrol. Anyone have any ideas?


Edit:

Update 2:
I tried plugging the bed thermistor into the extruder slot on the board, and LO AND BEHOLD, I got a temp reading! So I know I have a bad thermistor on my extruder, and that the board is fine.

Still one question then: Why does my bed read 0C when I plug the good thermistor into it?

 

Things tend to misbehave in strange ways when the extruder measures 0C. I think that's like the most important check (naturally) and the firmware will shut down a lot of other features until it sees a thermistor temp.

At least that's the trend I've seen.

 

That definitely makes sense!

Thanks a ton for the help guys, hopefully I can sort this all out with a fresh thermistor.

 

Thank you so much!!! This helped me out a lot. I did the same process and got the same results! Now I know what the problem is with mine.