I have been trying to learn HVAC for some time on my own. After taking several classes, I do have my universal license. I am stuck learning mostly from a book except for the ocasional help from the HVAC pro's that help me out at my factory. I am attempting to fix a humidifier that someone threw away just to see if I can. It is a couple years old. I have cleaned the condensor and evaporator, (which I normally do before starting to trouble shoot anything) When the unit starts to run the capilary tube between the evaporator and the condensor starts to frost. The frosting starts at the evaporator entrance and moves towards the condenser. Based on other experiences I think the tube may be plugged. Is this valid? It doesn't appear to be leaking. Anybody what to give a Newbee some advice? Thank you.