Auto Tuning the HotEnd

[maready]

I have everything completed....... I think.......

All motors respond to repetier fine.
I had to reverse the extruder motor in the firmware.
I have my Z height defined, and X,Y,and Z all moving to within .05mm of the table top. (How accurate do we need to be? I used an indicator in the pen holder.)
My hotend does heat up and Repetier monitors the temperature.
My heated bed warms up, the LED lights up, and Repetier monitors the temperature.

My Problem : As described on the wiki site, when Auto Tuning the hotend, I enter M303 S200 in the manual control tab, and get an error. "PID Autotune failed! Temperature too high. Error:checksum mismatch, Last Line:325 Resend:326"

This happens approx 3 mins into the process and Repetier shows the hotend at approx 221 degrees.

Please let me know if anyone has any ideas, fixes, sarcastic remarks, whatever you have that can get me past this last step!!!

Thanks........

[maready]

I got out a infrared thermometer out just to see what it would show.

For now I have the hotend set for 230 degrees C, and the heated bed set at 75 degrees C.
When heated, Repetier shows values very close to those above. They fluctuate a little but hover around these values.

The Thermometer showed the hotend at only approx 108 degrees C, and the heated bed way up at approx 102 degrees C.

Any ideas? Bad thermistors? Wrong thermistor values or type set in the firmware?

[Polygonhell]

Most IR thermometers read over much too large an area to give you an accurate temperature reading for the hotend, you'll need to use a thermocouple on a multimeter to get an accurate reading and ideally you should read it on the inside of the hot end.
When it's at 230 can you manually push plastic through it?
if so your IR thermometer is just giving you a bogus reading, I know mine won't read anything close to the actual temperature of the hotend.