Temp Reading Error

[Brandon A.]

Hi All,

I'm experiencing an error sensing temp on a R2X, stock firmware (I know, shame on me).

Background: 

A while back a couple prints ended up with cooked looking filament and eventually a clogged nozzle.  Upon replacing the nozzle I discovered the cause of the error to be the thermocouple "floating" in the well, making poor contact and therefore reading erroneous lower temperatures.  I attempted to improve the contact, secured the cable to the well as best I could, and tried it out.  Normal performance for a handful of prints and then I noticed pre-heat duration starting to climb.  I suspected this to be my repairs undoing themselves and stopped using that extruder (needed to get a number of prints cranked out on a timeline).

So I finally got some time to revisit this problem and decided the best course of action was to replace the thermocouple.  Yes, this was a foolproof, simple fix.  I was especially careful to hold the new thermocouple static and rotate the hot block around it to avoid damaging my brand new thermocouple.  Cool! Problem solved!  Nope.

Issue:

Ailing hot end cannot preheat above ~160°C (as read by printer).  Reading is not accurate, I suspect this 160°C temp represents the max temp the heater is able to reach under normal operating conditions.

I threw a calibrated probe on the side of the nozzle and found it to be ~230°C @ 160°C printer readout.  This leads me to believe the heater is not the issue. The other hot end heats and reads temperature as expected, this leads me to believe electronics / firmware are not the issue.  Is it possible that I received a bum thermocouple (or did in fact damage it during installation)?  Most likely I believe heat is not transferring to the thermowell efficiently.  I plan to heat the thermocouple outside of the hot block and compare back to the calibrated probe.

Is there anything obvious I am missing?  Any other suggestions for isolating the error?  If my test confirms my suspicion what is the best method for improving thermal transfer from the hot block to the thermowell?  

Thank you in advance for any input.

-Brandon