Avoiding Customer Dissatisfaction
I'll second suginami's post--I previously mentioned that I have tried the dealer and three independents in the last ten years.
The dealer was greedy and the techs that did the work couldn't care less about quality. Perhaps it was more of a morale problem there.
The independents mostly did not seem to understand business--in that being fair with customers is what promotes customer loyalty. Charging for parts not replaced, using old parts while charging for new, lying to customers over trivial matters, I've seen it all. I believe those independents were not completely dishonest, but they put themselves in that position because of incompetent business practices. Few, if any, businesses get ahead by a policy of dishonesty.
Customers should understand when the labor for a remove and replace job seems high, especially when the shop points out the particular difficulties when the customer pays the bill. If the customer complains, that is his perogative and if he does not come back, so be it. As stated before in this thread, those things happen.
Naturally, customers should be made aware of the nature of troubleshooting, and the technician should keep him informed, but diagnosis is always tough to call, making the policy of customer confidence all the more critical. My business uses an escalation policy to involve more skilled staff and the attention of management if progress is not made within a particular time frame. This is more for the customer's confidence than for the efficient use of staff, but it is also a good policy to avoid excessive charges when a tech has a bad day.