My A/C system was not putting out cold air, and has needed to be refilled 3 of the last 4 years so likely has a leak. Based on previous reviews, I contacted Controlling Systems to proactively service the system. The technician couldn't have been nicer or more knowledgable. He gave two options to locate the leak: the expensive, but relatively fast full system review, or the less expensive use of a dye/small leak repair substance. This would take longer to locate the leak, but the substance might plug it without further repair needed. The technician's practical advice was much appreciated, and I couldn't be a happier customer.