I wanted to ask (honestly) the more experienced techs on here there opinion. I am a installer with 17 yrs. experience. In the past couple of years we have gotten new service techs at our shop. They claim that flux can actually crystalize and plug the piston causing high head pressure. I think sometimes they simply dont know what is wrong with the system and use this as an excuse. I have never heard of this before and think these guys have my boss totally snowed!! If I am offbase let me know. I just want to know the truth. I cant see flux plugging the piston it doesnt make sense to me!! Thanks for the responses!!