Thermistor Issues (Max Temps / M999)

The Solidoodle has a variety of methods to protect the printer from overheating. The printer must a consistent and realistic temperature in order to function, and will go into emergency shut-off mode in the case of dangerous looking values.

If your printer steps working suddenly, and reads

stopped due to errors, press m999 to restart

You may be having thermistor issues. The message is telling that the Solidoodle has been put into emergency stop mode, and that by entering m999 into the g-code console the printer can be restarted. Often in these cases the printer will read 0 c - indicating that temperatures are not being read correctly. Alternatively, the printer may be reading a massively high temperature. In either case, the printer will be rendered inoperative until the problem is resolved.

Most commonly the issue is due to an open circuit somewhere in the signal path of the thermistor itself, all the way to the connection to the motherboard. The thermistor is located on the Hot End and it's connector is labeled "ET (Extruder Thermistor)"

Keep in mind, there are two sets of connectors to the extruder thermistor. One on the Hot end and one that connects directly to the motherboard. There could be intermittent connectivity due to a breaking wire. This may not be visible due to breakage underneath the wire insulation. Another source of failure would be where the wires come into contact with the connectors. Sometimes they may come loose from the connector and you will have to push them further into the connector. You can do this with two kinds of tools

A T-handle or
A Wire Crimper

However, the wires can often be pushed in with a simple bobby pin, or desktop pen. In certain cases the connectors can simply be plugged and unplugged to get the desired effect. The best results can be found by doing thorough investigation with a multimeter - looking for loss of connectivity at each wire juncture.

The thermistor itself is very rarely damaged, and the problem is nearly always the wiring.

If you are unable to get rid of the M999 Error, please contact support:

support [at} solidoodle [dot} com

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