We have a problem with the PLA not feeding after about 45 minutes. We have a R1+ with a new Ramps board and new hotend (inc thermistor and heater). We are using PLA at 210 C. The PLA stops feeding even while the hobbs bolt is rotating. We sometimes find a bubble in the PLA at the top of the hotend which stops the feed but we don’t hear the hobbs bolt clicking or see the nicks in the PLA. The hot end cooling fan is warm to the touch. When I try to pull the PLA back out of the hotend while the temp reads 210 C, it acts like the hot end is not hot enough and the PLA sometimes breaks leaving a curled section about the length of the hotend tube. Attempts to measure the temperature externally (handy steak thermometer) indicates the temp is at least 186 C. (I don’t think there is a good thermal connection so I think it just indicates the temp is high). The PLA bubble and warm fan makes me wonder if the hotend has heated up too much at the top so it is not filling the reservoir at the bottom. Any suggestions? thanks to Mark. When we removed the hot end cooling fan its bearing were not good. It would rotate but slowly. We are replacing it with a new one. problem solved.