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I have a Monoprice Maker Select bought at the end of April '16. It is a 2.0 Wanhao i3 equivilent level. For some reason, the hot end temperature logic on the board is not accurate. A few weeks ago, my hot end got astronomically hot and started turning my PLA black and bubbly mid-print. The display said it had dropped from 230 to 180 degrees, and the printer kept trying to get hotter. It burned out my heater cartridge. I replaced both the cartridge and thermistor, and still the same situation. I tried to run a PID autotune, and it times out because it can’t get to the 220 degrees. It was around 195 when it timed out, so I quickly swapped the wires with the bed thermistor… the display said the bed was 315!!!

When I turn the printer on from cold, the hotend says it is about 57 degrees, while the bed says 25. I hooked another thermistor up to the heating block and plugged it into the bed, then tried to preheat the printer. When the hotend temperature says 92 degrees, the bed thermistor says 210 degrees!

I’ve swapped around thermistors, and it is a problem in the logic board/unit. Any idea if this can be corrected via software, or is it a hardware issue? I sent Monoprice support a mail yesterday.

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Once my thermistor’s leads broke so I used a temporary replacement. It didn’t fit very well and was being cooled by the air. I had no special tapes so I plastered it for that time period. If I was you I would check the firmware first. If no issues, put the thermistor on the heated bed and see what it says. Don’t forget eeprom overrides the firmware.

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Hi John,

This sounds like the hot end temperature is being calculated based on a different thermistor. I don’t know about your specific printer, but on other printers I’ve used there are various thermistor options available.

Kind regards

Tom Hinkley

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Thanks a lot for the reply, Tom. I replaced with a like thermistor, 100k. I also swapped the original thermistor back in, and same readings! I’m hoping it is a EEPROM tweak I can make and not a bad Melzi…

-john

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Thank you… I will try the thermistor on the heated bed and see what it says; fit seems OK, but I hadn’t thought about using that as another constant.

Any idea what I should look for in EEPROM config?

-john

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Pid drive min should be low. Mine is 40.