Same exact situation in our office.Lets revive this thread
I used to have a no fix, no fee. That has been changed since a year ago.
Now I charge a diagnostic fee but waived it if serviced. Why do I do it? Simple. A client comes in, I find the solution, whether or not I personally can fix it or not, the client decides not to "fix" it, takes that knowledge to the neighbor and they fix it for free.
The point is, I provided a service, regardless of the outcome.