On the one hand those service men have their instructions they violate for their own benefit only: you should let them do their job.
On the other hand some of them appear to believe bolts and nuts are some "gadgets" to be turned with a master computer rather than a wrench.
Once I tried to replace my current car's cabin air filter myself. It's a simple procedure minding limited access in the passenger's foot well. Being a clean freak I declined kneeling and accidentally extracted the cabin fan instead.
I put it back but it stopped working. Feeling a bit tired I called the official service just to be told they'd have to do some computer diagnostics. "-Look, I just told you...". They hung up.
I said what they refused to hear aloud and fixed it myself by reinstallation of the fan.
Or most recent. I found my "
underbody panel (#7)" hanging down. When having the car serviced I pointed that too. They listed some "diagnostics" (at a price of a computer one, at least!
). "-I've diagnosed it myself. I just need it (fucking) fixed! -All right, we just have to charge something...". It went like that: the mechanic diagnosed missing clips. I called the service man and he told him to fix it (for free).
