Unresolved Bed Max temp error

Hi all! I have a problem that is making me nuts...I have a R1 with the bed that has 4 magnets and a grey cabel. I have been trying to find the fault with my bed. When i start a print or trying to prepear it i set the heating values and both the hotend and bed starts to heat up, but they rise nearly equal in temp at the same time and all of a sudden the bed goes up in temp beyond the set value. Then the max temp error kicks in.
I have checked the cabels (grey quite stiff one) the connectors, changed both the thermistors (bed and hotend) measured the cabels and thermistors with a multimeter both before and after the change of them. I bought the R1 used, the guy that sold it to me started it up and showed me it worked. But when i got home i didnt work. I have a Velleman K8200 that i build my self so i got some experince in 3D printers. I have been trying to use several different program with diffrent resaults (cant get the machine to connect al the time) RepetierHost, Cura, Mattercontrol, Simlify3D and even the Xxl LCD and nothing works... I can understand if my text maybe is a bit confusing but i am from Sweden so English is not my native tongue and my school English sux, but i my understanding i reading is much better then trying to translate my toughts in to English words.

Please try to help me or if you want something explaind in a differrent way i would try to translate it bettet.

Thank you in advance
Matte

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Thanks for your reply..
The original thermistor was not broken, i tested it with a multimeter but even changed it just to rule out that it wasn't faulty or that my readings were wrong. I get the samt readings with the new one, around 103ohms when cold and it changes when i warm it up. When i tried to heat the bed i had i put to 60° celsius. Even tried with 50° and to change the settings in one of the programs (dont remember witch) to not have a heated bed, but i dont know if took effect. I have checked the wierings both connected to the board, without it connected, with the connector disconnected in both ends. I cant find any shortings in cabel or the connectors.
I was thinking about to change the connector position for bed temp on the board to the second extruder temp, but i don't now where in the firmwere to change that setting. I have tried multiple firmweres too, but now i can't even change firmwere. It says Robo3dr1v3 on the lcd display. And i don't know what i am doing wrong beacuse i can't change it again. I have the latest version of Arduino program, i have read that an older version works better but i didn't had any problem so far, until now will say.

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IF YOU HAVE GREY CABLING REMOVE THE CONNECTOR BEFORE GOING ABOVE 85C OR ELSE YOU RISK FIRE DAMAGE.

Sorry for the emphasis, just need to make sure that's clear

 

could one or both thermistor be non stock and the firmware set for the wrong ones?

 

@ William Muraski
The printer worked when i was at the guys house that i bought it from. He showed me by starting it and heating it up and it worked.
To my knowlege it had the stock thermistors. But when my problems started i swapped them out to new ones. The hotend has a thermistor from a Velleman K8200 (100k/ohms) it was what could find fast enough in town.
The bed thermistor is from E-bay (china?) It was rated to 100k/ohms. Both of the thermistors should be like the stock ones, at least i get the same readings when measureing them (old and new).

@ Mike Kelly
I have seen pictures of peoples misshaps with that thing.
I do not plan to get that high on temp just get it work to begin with =P.

@ Mark Tomlinson
Can i check the RAMPS with a multimeter? Or do i need to just change it to a new one?

Thank you all for your help =)


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disconnect the temp sensor for the bed from the RAMPS, then in the software try and heat both up again and post what happens.

 

Can i use my LCD screen to do that or is it better to use the USB cabel and a computer.

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i am not sure as i dont have an LCD, but what i am looking for is with the bed sensor disconnected does the software/display show the bed temp to raise the same as before (with the hotend/nozzle) if it does it will error out no worries but it would show that it may be using just the hotend/nozzle sensor for both and that can happen in 3 ways, wires are crossed that shouldn't be, or something is corrupted in the firmware, or something is going on with the LCD display/controller.

4 ways, add a PID configured wrong.

 

This helped thanks! I was printing at 110c bed temp per matterhackers suggestion and bumped it up a few degrees and now it works.