My land lord called TDI air conditioning when I had a problem with my in-attic air conditioning unit. While each of the repair men was friendly and courteous, it still took multiple visits for them to figure out a simple problem with the electrical relay in my unit. I'm certainly no expert, but the symptoms never changed and I would expect a big-name company to be able to diagnose a problem in less than 3 visits. I did without A/C for an entire weekend while waiting for Monday morning since it's too hot in the summer for them to go into an attic to repair a unit. While I understand their point, it was still very aggravating and inconvenient.