Our Replicator 2 printed well out of the box two months ago; now not well. We’ve tried leveling the build plate, cleaning the motor, unloading and loading the filament, changing the filament. No go. Now I am searching the web looking for solutions and got a kick out of this post on a Maker Bot Operators group on Google Groups. I identify with this guy:

I received my Rep2 in late October and had GREAT prints – worked freaking well.  Then came December 12th.  It went south and went south quickly.   I’ve had leaky extruders, MK8 Modification, 4 spools of PLA from different suppliers – you name it, I tried it.   I couldn’t get a good print to save my life – like many of us on this forum.  It just wasn’t working.  AirPrints in about 10 % of the build, etc.    I even replace my extruder out of my own pocket from the one from QU-BD (they sell a MBE replacement – looks like the same one MBI uses).  Anyway, prints that use to print were not even printing.  So yesterday, after reading posts from both Dan and whpthomas (both of which are great guys) and reading that both of them are PhD’s, If two PhD’s can’t figure it out, I’m doomed. I was about to throw in the towel with Makerbot.   So I grabbed some coffee and sat thinking about returning my once loved Makerbot Replicator 2.  I was really bummed.   As I sat pouting with my coffee it hit me.  I’ve tried everything with degrading results and when I reverted back to the original extruder, I had the same, nozzle jams.  I read about lowering the temperatures and have tried all temps from 190-230 all resulting in bad prints.    BAM- I’m assuming the temperature is accurate.  What if my 230 is really 190?  I doubt it but it was worth a try.  So I pull out my trusty Flir and sure enough – the Rep2 is reporting higher temperatures than actuals.  So I changed my geode to set the extruder temperature to 242 C and printed.   100% Success!  I’ve been dicking with this several weeks with 100% failure rate thinking it was everything from bad PLA to planetary alignment.   It looks like the heat sensor has lost its sensitivity over time.

If you’re having the nozzle stop on you mid build, you may want to try cranking up the heat rather than decreasing to see if it helps.   I’m attaching my thermograms to show the results – the temperature on the bot was set to 242 C.  Page was shows the heater block at 211.6 C and page two shows the Nozzle temperature at 148 C !    Reflectivity has been set for both the insulation and the brass nozzle.  Increasing the heat solved my issue. So in short, I’m seeing 211.6C when I set my bot to 242!  
I’m off to update my ticket with MakerBot but so far, I’ve made HUGE progress by simply increasing the heat.   
I hope this helps!
Now I will figure out how to adjust the temperature.