Upon arrival in Elgin, I performed the A/C cooling evaluation and found everything operating properly at this time. During the evaluation I found that the heat transfer media system is dirty. Spoke with the customer about their different options for cleanings and they chose to go with HK2A. Will need to schedule a time to come back 1 tech 1 hour. There is a small spot in the return at the air handle that needs to be sealed when we come back out.