Well I found part of the answer. If you have too much generally applied cooling, the heater in the nozzle assembly cant keep up with the demand. I put my USB fan too close and the bed temp and extruder temp would not reach the set point. I could not explain why when I raised the extruder, It reached temp and lowered it it would not. thought loose temp sensor wire or something. called in my wife and she said, is it that fan! duh!