MAXTEMP error at startup

I am new to the forum but have been reading it for months and find it very helpful.
I have build a large printer running with a Rumba controller and DRV drives and Marlin firmware my problem is when i power up the printer it immediately tells me there is a MAXTEMP error and the print was halted and it needed to be reset.
I am in need of some assistance.

I saw this happen on my printer before when I was first configuring the firmware. I had the wrong temp sensor. Once I picked the correct sensor type, the temp registered good after that.

Chances are it is either an incorrectly defined sensor type, or a connection/wiring problem.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

The MAXTEMP error is a fail safe programmed in Marlin to shut down the printer should the thermistor become detached from the board or if the thermistor wire breaks (which does happen over time). When the themistor is detached the board registers a value of 0^oC. The printer will continue to heat until 0^oC equals your set temperature which will never happen, thus it will heat until your ceramic heater burns out, your printer burns up or your house burns down.

Other issues could be that:

1) Your connector for your thermistor is not seated correctly to the pins on your board. Take off the connector and reconnect it.
2) Your thermistors are attached to the wrong pins. I have seen a situation where a fellow poster attached a thermistor for Extruder_0 (Temperature_Sensor_0) to the pins for Extruder_1 (Temperature_Sensor_1) and another where the poster attached the thermistor for the heatbed to the same pins. In either case you get a MINTEMP error.
3) Your thermistor is bad
4) your board is bad.

These are the typical thermistors that are used with hotends and heat beds:

[www.ebay.com]

Do yours look like these? If so in Marlin your setting should be set to 1. That is:

#define TEMP_SENSOR_0 1
#define TEMP_SENSOR_1 0
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 1

assuming you are using only one extruder.

Edited 2 time(s). Last edit at 12/01/2016 11:20AM by Lymphomaniac1.

Thank you Lymphomanic1
My Marlin setting looks like the once you post. I will check the wiring and the type of sensor is the right one according to the supplier but will make sure myself.

The type of Thermistor I showed is the one you need for the settings I provided. If yours look different, replace them with ones similar to the ones shown.

Another thing that can cause a MAXTEMP error is a dead short either at the tip of your thermistor (defective thermistor) at the terminal connectors or in your board (defective board). Change out your thermistors first, they are the cheapest thing to change out. Use ones that are pre-wired and have a connector at the end. See:

[www.ebay.com]

Thanks for all the help.
I found the problem sensor was bad.

I had a new thermistor go bad and now every one I connect gives me this error. I think it may have screwed my controller board... Anyone know if any other pins can be utilized for the hotend thermistor to see if it is just those two pins?

Try the reset button on the control board, there is a lockout after a thermistor failure.

Can a maxtemp error show if a board has a problem? i connected my thermister, and see a maxtemp error. When I short the thermistor, it shows 0 degrees celcius. Without the thermister, shows 500 degrees. with the thermsiter, or a 100k resistor, it shows about 470 degrees. I changed the power supply by thinking maybe the power was not enough (was testing with a 800ma PS). i fried the board by reversing the polarity by mistake. But was my board bad to begin with?

You might just have the wrong type of thermistor selected in the config.

If it is configured for a standard thermistor 100K resistor should show room temperature. Sounds like a wrong thermistor was set in the firmware, or you had an electrical problem.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]