Several months ago after slightly reworking the wiring to the J-head, the thermistor slipped slightly loose from its socket in the heater block. The temperature monitoring code in the controller will detect a short or open connection on the thermistor and shut down the heater, but it can't do anything to detect a thermistor that is simply no longer thermally connected to the block, and the heater stayed on long enough to drive the heater block far above its normal operating temperature. I...
