Thermistor ohms check HELP!!!

Ok guys. I have been on reprap irc and can not get any help. looks like I am invisible. I have or thought I bought some EPCOS 100k thermistors. When I check them all at room temp I get 69.6k. My shop is pretty hot so take that into terms also. I am having trouble with my hotend jumping 20c above what I set then it comes down. I am running ramps 1.4 and marlin ferm. I can not do the M303 command because it gives me a hightemp error almost right off.
Please help.
Steve

Steve,

A hot shop could make it read that resistance, yeah. If you're overshooting the set temp, then stabilizing, your PID settings are too high. In marlin, you can do a PID autotune form room temperature by sending M303 S150, that will set the temp to 150 and run the autotune, and give you the new PID parameters to set in your configuration.h file. If you're getting maxtemp right away, maybe check your connections for a loose or shorting wire?

Thanks Johnoly for replying. Right now it has cooled off in my shop and I am reading 93.4k. I have tried to run the m303 s-150 and get a high temp after a few seconds. It takes a few to reach temp but over shoots like 20+c. I am at a lost. I am running a 24v 15a ps. Maybe my amps are too high. Also the heater is a 6R8 ohm.
Thanks Steve

does it overshoot and stabilize? lower the pwm power level to 160. have it heat a little slower but not overtemp as high. temp should stabilize after overshoot, or pid calc needs to be recalculated.


if above does not work well then
lower this value

#define K1 0.95 //smoothing factor withing the PID

to
#define K1 0.45 //smoothing factor withing the PID

and keep lowering it until temp can stabilize.