[bigglywiggler]

I am a qualified mechanic. I no longer work in the field but I did for many years. Typically, when people 'trust their instincts as a user' they are fantastically wrong. Off by a mile. They have little to no idea how a car works besides youtube videos and forum posts which are full of inaccuracies or outright nonsense and they don't want to pay for diagnosis.

So when they would come in asking for a specific part to be replaced with no context I used to tell them that we wouldn't do that until we did a diagnosis. This is because if we did do as they asked and, like in most cases, it turned out that they were wrong they would then become indignant and ask why we didn't do diagnosis for free to tell them that they were wrong.

Diagnosis takes time and, therefore, costs money. If the user was capable of it then they would also be capable enough to carry out the repair. If they're capable of carrying out the diagnosis and the repair then they wouldn't be coming to me. This has proved to be true over many years for everyone from kids with their first car to accountants and even electrical engineers working on complex systems for large corporations as their occupation. That last one is particularly surprising considering that an engineer should know the bounds of their knowledge and understand how maintenance, diagnosis and repair work on a conceptual level.

Don't trust your instincts in areas where you have no understanding. Either learn and gain the understanding or accept that paying an expert is part of owning something that requires maintenance and repair.