pid autotune bed failed

hi, i'm finishing my first self made prusa and i'm at the PID autotune point of the build.. Ive managed to autotune the extruder, which now gives me a nice oscillation of 1 degree, but the bed temp is still swinging violently so i figured i'd autotune the bed too...
the thing is that it keeps giving me the temperature too high message, even tho my thermistor values are 28 for the head and 31 for the bed.
The command i'm sending is
M303 E-1 S60 C8
what is wrong?? i can't even find in the firmware the lines for the bed PID..
is there some patch or piece of code i'm missing?
Thanks

oh, nice. now the pid starts, but it heats up the extruder... now i'm thinking i'm really missing that piece of code on my firmware.. how can i tell?

That might the command for Marlin, but not for Repetier-Firmware. There it says:

M303 P S X0 - Autodetect pid values. Use P for heated bed. X0 saves result in EEPROM.

So for 1 extruder setup send

M303 P1 S60

X0 works only for development version.

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Quote
repetier
That might the command for Marlin, but not for Repetier-Firmware.

i use repetier-host.. not repetier firmware. i've tried with the P instead of the E and got no response.

The commands are interpreted by your printer resp. the firmware you run there. If it is not Repetier-Firmware you are seeking at the wrong place. That you send the commands from Repetier-Host does not matter in this case. The host works with several firmwares but you have to use the commands matching the firmware use.

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Repetier-Software - the home of Repetier-Host (Windows, Linux and Mac OS X) and Repetier-Firmware.
Repetier-Server - the solution to control your printer from everywhere.
Visit us on Facebook and Twitter!

oh. i thought the sub forum was for repetier-host. i actually didn't know there was something like repetier firmware!
thanks