Service diagnostic found that the thermostat had failed, it was receiving a constant 24 volt signal but the thermostat was not responding. I also found the drain line had a clog in it. The return air filter is dirty, I recommend replacing it asap to prevent unwanted stress on the system. On the outdoor system I found the fan motor is showing signs of wear and tear. I spoke with homeowner and she agreed to have the drain line serviced and sign up on our maintenance plan. I cleared, cleaned and treated the drain line and verified it is draining. Mr. Sweeney had bought a thermostat in case it was the problem. I replaced the thermostat and verified it was programmed correctly and started up the system. The system is now operational.