This is probably not a RAMPS issue, but since that's the controller I was using, here goes. My hotend (a J-Head) has been very intermittent lately. My printer has been working great for almost a year, but yesterday when I turned it on and started warming it up, the hot end wasn't heating up. I reset the arduino and re-established the connection, and everything seemeed to be OK. Again tonight, it wouldn't heat up, and it wasn't being responsive to the same reset process, so I set about removing the RAMPS from it's enclosure. Once I got it opened up, it started working again, so I started a print. I wasn't really paying attention to it, but a few minutes later I saw that there were several "Cold extrusion prevented" messages on my host software. I looked at the temperature graph, and sure enough there was a dip. It had recovered, and was working normally again, but there was a 20 second window where the temperature was low. After this, I was watching more closely. It never got cold enough to prevent extrusion again, but there were several temperature dips. When things were working fine, I noticed that the LED next to the MOSFET was flashing. When the temperature would start to dip, the LED would come on solid and it would remain solid even though the temperature would continue to go down. Several times it got pretty close to the cold extrusion threshold when the temperature would start to rise and the LED would start to flash again. The LED behavior tells me, I think, that the thermistor is working OK. It just seems like the resistor is not putting out heat when the MOSFET is on full. It seems to me that if the problem was the resistor, or the MOSFET, it would just fail and stop working altogether. I'm hoping it's just the wiring - a loose screw at the terminal block, or perhaps a bad in-line connector near the extruder. Now that things are open, I'm going to very carefully make sure everything is secure, but if anyone can offer any other advice based on my description, I'd appreciate it. Thanks. https://reprap.org/forum/read.php?219,209310,209310#msg-209310 Thu, 13 Aug 2026 20:05:37 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?219,209310,209364#msg-209364 https://reprap.org/forum/read.php?219,209310,209364#msg-209364 lazzymonk RAMPS Electronics Fri, 17 May 2013 02:08:55 -0400 https://reprap.org/forum/read.php?219,209310,209310#msg-209310 https://reprap.org/forum/read.php?219,209310,209310#msg-209310
My hotend (a J-Head) has been very intermittent lately. My printer has been working great for almost a year, but yesterday when I turned it on and started warming it up, the

hot end wasn't heating up. I reset the arduino and re-established the connection, and everything seemeed to be OK.

Again tonight, it wouldn't heat up, and it wasn't being responsive to the same reset process, so I set about removing the RAMPS from it's enclosure. Once I got it opened up,

it started working again, so I started a print. I wasn't really paying attention to it, but a few minutes later I saw that there were several "Cold extrusion prevented"

messages on my host software. I looked at the temperature graph, and sure enough there was a dip. It had recovered, and was working normally again, but there was a 20 second

window where the temperature was low.

After this, I was watching more closely. It never got cold enough to prevent extrusion again, but there were several temperature dips. When things were working fine, I

noticed that the LED next to the MOSFET was flashing. When the temperature would start to dip, the LED would come on solid and it would remain solid even though the

temperature would continue to go down. Several times it got pretty close to the cold extrusion threshold when the temperature would start to rise and the LED would start to

flash again.

The LED behavior tells me, I think, that the thermistor is working OK. It just seems like the resistor is not putting out heat when the MOSFET is on full. It seems to me

that if the problem was the resistor, or the MOSFET, it would just fail and stop working altogether. I'm hoping it's just the wiring - a loose screw at the terminal block, or

perhaps a bad in-line connector near the extruder. Now that things are open, I'm going to very carefully make sure everything is secure, but if anyone can offer any other

advice based on my description, I'd appreciate it.

Thanks.]]> jbernardis RAMPS Electronics Thu, 16 May 2013 20:37:19 -0400