If your 3M EC glue gun has low or no adhesive flow 62-9680-9730-3 EC Heat Block Repair Kit might be just what you need. The low or no adhesive flow could be caused by gelled adhesive in the heat-block or valve.  Replace these parts and hopefully your problem will be fixed. The 62-9680-9730-3 includes heat block assembly, valve assembly, trigger pin, nozzle, insulation, handle screws, and end clip.