My father always urged me to “be part of the solution, not part of the problem.” I can remember being at someone’s house working with dad on a piece of builder grade equipment that someone else put in. I remarked out load about the cheap brand furnace they had and was quickly and forcefully reprimanded. “NEVER insult the customer.” In dad’s eyes our job was to fix a mistake they had already made. He built his business by being part of the solution. People remember who helped them out of a jam and offered solutions to their problems.
Always try to keep the conversation positive. If you have identified problems, present solutions. Never belittle the customer for a poor decision they made. Instead, offer a better way or a way out of the problem. Never badmouth previous companies and techs. Instead, focus on your solutions. If the issue is a safety concern, you should certainly explain the risk, but offer a solution. In short, focus on solutions, not problems. Your job is to help the customer solve problems, not point out all their shortcomings. Dwelling on mistakes of the past, no matter whose they are, only leaves the customer with a negative feeling. Worse, they associate you with bad news and don’t want to see you again. Focusing on solutions and remaining positive makes the customer feel better. They associate you with good news and solutions. If you do this, I guarantee you customers will start asking for you by name. There is no better job security than having customers calling in and asking specifically for you.