Extruder Heater: Reaches Temp, then termistor not readable

Prusa Mendel w/Wades Extruder (3mm PLA)
J-Head Mk IV-B (0.5)
Heated Bed
RAMPS 1.4
Kliment-Sprinter (Arduino 22)
Skeinforge
Printrun Pronterface
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We just recently got our printer working. Had a couple days of some very fun un-sloppy printing.

About a day ago, the heater port (D10) LED started blinking shortly after reaching the target temperature (in Pronterface).

Now the extruder heater just reaches the target temperature and shuts off. About 1 minute later, Pronterface starts reading the temp again.

I tested the thermistor value after I quickly pulled (fun) the heater bed & extruder thermistor connector and tested the resistance.. It read 2.xxx k ohms.

I let the extruder thermistor cool down while testing the Ohms, it wet back to ~100 k ohm.

Even rechecked and reloaded the firmware.

Anybody have any ideas?

There is an over temperature protection in the firmware. It shuts down the hot end if it goes over a set temperature. It can do this mid print which is a pain. My printer worked fine for weeks , then I had this issue. Its probably due to interference in the cabling when I resited my printer. There are reading spikes from the thermistor, one of which triggers the over temperature protection.

Check your firmware. I have my temperature protection set up to around 275 degrees I run ABS at around 255 degrees so this seems about right. Also switch on "temperature smoothing" this averages out the readings so you dont get high temperature spikes.

I think this helped a lot, I noticed the temps were a little low and I think my molex connectors for my extruder are sub-par. lol... Need to find a proper crimping tool for sure.

Thanks for your help!

The heat could be affecting the connection of the thermistor at the hotend side. you can make a very good connection without crimps by wrapping the 2 wires to connect around each other once then tightly back around themselves.

It could also be shorting to the heater wires