heated bed false thermal runaway issue

I'm starting to run out of ideas.
My printer started stopping mid print while running marlin 1.0 . So I thought i should upgrade to the marlin 1.1.5 firmware (my thinking was Simplify3d was having a problem with my old firmware plus Repetier host wouldn't work at all)
This did not fix my stopping mid print problem. however Repetier host did start working.... small victory's.
On a side note I did change both the ramps 1.4 board and the mega.thinking if it was a faulty mosfet on the ramps that would sort it

After looking on the forum for people with the same problems I found the Thermal Protection parameters section in the configuration_adv.h

If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
* WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
*/
#define WATCH_BED_TEMP_PERIOD 160 // Seconds THIS WAS 60
#define WATCH_BED_TEMP_INCREASE .2 // Degrees Celsius THIS WAS 2

As you can see I've changed this quite a bit. unfortunately it does not make any difference to the problem.
Today I tested the heating again. the bed was set to 90 degrees. The bed hit 90 degrees. Then got to 92 then seemed to drop to 87.70 then the dreaded .READ: Error:Thermal Runaway, system stopped! Heater_ID: bed
READ: Error: Printer halted. kill() called!



So all I can think it could be with my very limited knowledge of firmwares and electronics is

I did think about turning the bed thermal protection off but I don't think that is fixing the problem just side tracking it plus id like to not burn my house down.

Faulty bed thermister
heated bed mk2b alu
power supply loosing power 12v 360watt

all of the items above are over 2 years old. Can/do they wear out?

Quote
Adrenalized
I'm starting to run out of ideas.
My printer started stopping mid print while running marlin 1.0 . So I thought i should upgrade to the marlin 1.1.5 firmware (my thinking was Simplify3d was having a problem with my old firmware plus Repetier host wouldn't work at all)
This did not fix my stopping mid print problem. however Repetier host did start working.... small victory's.
On a side note I did change both the ramps 1.4 board and the mega.thinking if it was a faulty mosfet on the ramps that would sort it

After looking on the forum for people with the same problems I found the Thermal Protection parameters section in the configuration_adv.h

If you get too many "Heating failed" errors, increase WATCH_BED_TEMP_PERIOD and/or decrease
* WATCH_BED_TEMP_INCREASE. (WATCH_BED_TEMP_INCREASE should not be below 2.)
*/
#define WATCH_BED_TEMP_PERIOD 160 // Seconds THIS WAS 60
#define WATCH_BED_TEMP_INCREASE .2 // Degrees Celsius THIS WAS 2

are you sure that the bed define change is 2 and not 0.2 as it looks in yours

As you can see I've changed this quite a bit. unfortunately it does not make any difference to the problem.
Today I tested the heating again. the bed was set to 90 degrees. The bed hit 90 degrees. Then got to 92 then seemed to drop to 87.70 then the dreaded .READ: Error:Thermal Runaway, system stopped! Heater_ID: bed
READ: Error: Printer halted. kill() called!



So all I can think it could be with my very limited knowledge of firmwares and electronics is

I did think about turning the bed thermal protection off but I don't think that is fixing the problem just side tracking it plus id like to not burn my house down.

Faulty bed thermister
heated bed mk2b alu
power supply loosing power 12v 360watt

all of the items above are over 2 years old. Can/do they wear out?

Answered in post disclaimer I am not a marlin user so I could be well off but it does look like your 2 is actually 0.2

I'll change it back to 2 from .2 and see how it goes. I think I read it wrong when I changed it. good spot!

after changing it back to 2 I turned on the heated bed .The temp got to 103 before it seemed to max out then trigger the same READ: Error:Thermal Runaway, system stopped! Heater_ID: bed
READ: Error: Printer halted. kill() called!

Edited 2 time(s). Last edit at 11/03/2017 09:25AM by Adrenalized.

is there possibly a max bed temp setting somewhere that you are hitting if so you may need to increase that a little to allow for your bed to reach your set temps?

Quote
dougal1957
is there possibly a max bed temp setting somewhere that you are hitting if so you may need to increase that a little to allow for your bed to reach your set temps?

Just checked its set at 150

Update.
Checked the resistance of the bed 1.3ohm :/
Removed the heater and made a new tin foil cork reflective insulator.
Fitted a mosfet board
My firmware was set to heat the bed using the bang bang method. Changed this to the PID method and did an auto tune at 90c

So far it has stopped halting for runaway errors.

Still takes ages to get to 115c but at least it gets there now.