I have 3 Unico 2 year old HVAC systems w/ exterior Bryant AC units that use Puron 410A. I have a smell like Crayola Crayons coming from one system. It started this winter when running the heat and is there when just the fan is running and when the AC is on. I've run it for hours to try and flush the smell out. The contractor can't find anything wrong with the system. But there was a dried pinkish substance in the drain pan (no odor). 3 questions: What does Puron smell like? What does it smell like after it hits a heat exchanger? Would the Pink residue have resulted from the Puron leak? Or from an oil leak? Or?