I have an early 1.0 that is a little over a year old.  I currently have about 950 hours on it.  At 450 hours I replaced the heater connector with a Deans connector. I am running stock firmware 1.1.G and I use Simplify 3D (although I had the following problem when printing the built in samples also).  I use an XYZ Pro resetter from WCTEK and have all updates blocked since the day I took the printer out of the box.

When I stopped using the printer a couple months ago I was convinced that I had a short in the harness somewhere.  My symptoms were that filament would cease to extrude after about 10-20 layers or so every print.  I would get clicking and then notice a little while later that the print head was above the print and no filament was coming out.  It wasn't a clogged nozzle as I could run a  load filament right after that and it would extrude with no problem.

The weird thing is that it seemed like the print head was keeping temperature the entire time.  That is why I thought it was just an intermittent  short.  I was busy with work and life at the time and didn't feel like trouble shooting it and was getting annoyed with this printer anyway after seeing what newer printers coming out could do, so I just shelved it (also I have Kickstarter funded a couple new printers that I am awaiting). 

My daughter is having a party at the house in a couple weeks and asked me to get the printer running again because her little friends like to see it printing.  I couldn't remember exactly what it was doing before, so I loaded it up and started a test print.  Sure enough after about 1/8" it stated clicking and then quit extruding, just going through the motions above what it had printed. 

It didn't seem like the last layer had bonded at all either, so I thought well maybe it is just way out of calibration.  I tried to run the calibration and it would get up to temp and then start to lower, raise the temp and then lower again, again and again.  It was getting hot enough, but it would never actually start the calibration. 

I turned it off and on again and tried and it did the same thing.  I thought maybe the last time I flashed the filament cartridge that something went awry so I pulled the cart and re-flashed it.  I reinstalled the cart and did a check cart.  It said it wasn't installed.  I pulled it out and put it back in like 5 times with the same result.  I tried another cart and the same thing.  While doing that, I realized that all this time that it didn't seem to care if the top door was open or closed and I thought I remembered it would alarm if the door stayed open.

I looked at the door sensor and it was kind of knocked loose.  I snapped it back in place and closed the door and low and behold it read the cart and gave me the stats.  I ran calibration and it immediately came back up to temp and started.  I am now printing with no issues. 

I am not sure exactly if my problem was that it hadn't read the cart, or if the sensor was only partially working??  I assume it is just a simple on off type switch that either works or doesn't, so who knows what it was, but now that the switch is back in place it is working fine.  I wish I had thought to check the cart stats before I pulled that first cart.  I assume it had read that cart at some point or else it wouldn't have printed at all. 

Next time I take the printer apart I suspect I will be bypassing that switch and will probably go ahead and flash the firmware with Repetier also at some point.