It is impossible to convince my sister that anyone can handle her HVAC unit unless qualified and licensed.
Her decision stems from the fact that she suffered serious consequences a few years back when a careless HVAC handyman broke her heat pump, forcing her to replace the AC when she was not prepared for the upgrade.
She decided never to gamble with the safety of her system after that and dedicated her time towards sorting for the right HVAC professionals, even if it meant paying more money. It turns out that benign this strict with who you hire to handle your AC and furnace repairs pays off eventually. She claims to enjoy continuously the peace of mind she gets when her system is fine-tuned because she knows that she will get through summer and winter without any hitches. Her system runs more efficiently and serves her better without incurring high monthly power bills. She is also sure that she can claim warranties for the system because it is being taken proper care of. Safety is never an issue whenever her HVAC technician is at work. She knows that he will do an excellent job and that the air quality in her house will always be top-notch. Finally, and most importantly is the fact that the HVAC contractor is always on time. There are no flimsy excuses. It is the guaranteed quality and professionalism that make her stick to the right professionals. With all these benefits, I may just follow her lead and get myself a good HVAC technician to call whenever my heating and cooling unit malfunctions.