Can you tell if your air conditioning and heating service technician has had proper HVAC Training? I can. After 30 plus years in the industry, including several years in the training side of the business, I can tell you straight-up that non-trained “technicians” troubleshoot by changing parts until they find the one that is broke. They will start with the parts that they know how to replace or that they “think” might be the problem. If you are paying by the hour for this “troubleshooting”, you have reason to be alarmed.
This by iteslf is an excellent reason to use companies that charge by the job, not by the hour. At least you wont be paying for this on-the-job training, maybe. My intent is not to trash service technicians who are trying to do their best to provide you with comfort. I admire all of the ones who really try. My intent is to point out the value of proper training, no matter what industry.