A service call fee is what an HVAC company charges to come to your home, diagnose a problem and give you a written estimate for the repair. 

When a technician is dispatched for a service call, there are a lot of expenses associated with that call that the average consumer is not aware of. 

In order for a technician to come to your home, the owner of the company has to take into account, not only the cost of having that technician available when you call, but also the cost of gas, automotive maintenance, office staff and more. In other words, an air conditioning company could never offer a free or low cost service call unless they were counting making their money back in other ways. 

Some people will always call the company that has the lowest service call charge, but it is important to understand that a service call is not a set amount of time and some companies charge in 15 minute increments. 

The charge for a service call should cover the cost of the technician coming out to your home and diagnosing the problem. Some companies offer a low price for their service call, but then they charge a diagnostic fee. Companies that offer very low prices for their service calls are usually just trying to get their foot in the door and they will almost always find some major problem with your system.