Problems with Folger Tech i3

Hi,
I have a Folger Tech i3 that Ive been having problems with lately. In Repeter its been saying both my bed and extruder temp are over 1000 celceus when there cold. Its saying temp error, reset using M999, something I dont know about. What is M999 and how do I reset it? Im guessing its something on the RAMPs board but Im not sure, I also have an issue with an endstop, its saying endstop not pressed when homing down, but it appears all of the endstops are pressed (the red LED is illuminating). Does anyone have any ideas how to fix these issues?
Thanks
Jake

M999 is Gcode (the code that your computer uses to communicate with your printer and execute functions on your printer) that can be sent in the terminal window of repetier. I have attached a picture of the location of this. Here is a link to other G Code. I would also check you have the correct thermistors selected in your firmware and that everything is connected correctly. The endstop issue could that your signal wire does not have continuity through it. Test for resistance with a multimeter on the green wire. I have had that issue with my Folgertech endstop and they sent me a new one at no charge.

As well as checking to make sure you're using the correct thermistor settings, I would check the wiring. Thermistors vary resistance with temperature: resistance decreases as temperature increases. A reading that high could indicate that there's a short in your thermistor wiring.

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Thanks guys,
I reentered all of the settings in and that fixed both of the issues somehow. However after a few successful prints my heated bed stopped working. I was fine tuning some of the settings so that may have caused an issue but after reattempting using stock it did not fix anything. My thermistor reading is showing a normal 22-27 degree range depending on the environment temp, but it does not seem to want to turn on. When I try to raise the bed temp manually it does not raise also, when it is raised I used to hear the psu fan ramp up but now I no longer get that. No errors occur or anything, so I don't think its software related. I don't have a multimeter so I cannot test voltages so I don't know if it is receiving power. I checked the connection to my RAMPS board and it is intact and normal as well as the wiring on the bed itself. Could anyone help me figure out what might be wrong? I am going to try and pick up a multimeter but I don't know when I can get to a hardware store so if anyone could help me out now and get me back printing I would appreciate it.

Pull the heat bed power input conector off the RAMPS and have a look. The poor quality Chinese knockoff Molex connectors overheat and burn very easily, and this is what happens, and you often can't see anything from the outside. Barring that, the only other component in the power path is the MOSFET . . . You should also see a red LED go on and off with the heatbed channel on the RAMPS. Oh, and lastly, make sure your changes didn't get stuck in EEPROM -mif yiu were playing with PID tuning on the bed, those do live in prom, and override what is in your upload.

- Tim

Cheap Chinese Mosfets also tend to burn out. There are three on the board; two quite close to one another and one close to and with its back to the power connectors. The latter is the one for the heat bed and the one that tends to burn out. If you have any discoloration or melting of the power connectors, chances are your heat bed mosfet has burnt out.

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[3DKarma.com] - suppliers of quality, affordable 3D printer kits and filament for the UK market.

I've seen these connectors fail due to not much more than looking at them from an angle . . . that, and there is no possible MOSFET fault that can draw more current through the connector than what is drawn when the MOSFET is on . . . so very little to no relationship between the two . . . but yes, both are possibilities, as I already mentioned . . . Also, MOSFETS typically fail locked on (shorted) and the problem here is no heat . . . .

- Tim

Edited 1 time(s). Last edit at 08/06/2015 12:20AM by tadawson.