Upon arrival system had no filter. Checked stat out and it is an older mercury stat. Turned it on cool and blower came on. Went outside, found system low on refrigerant but one cap was off the true suction port and there was oil around it. Spoke with customer had he approved adding refrigerant. Got pressures up. Went to crawl, coil and blower are clean, found no leaks inside. Wires all tight. Drain is clear. Went outside, cleaned coil. Contacter and capacitor checked out good. Fan and compressor amped good. And refrigerant levels are now good to go. Added 3lbs of 410a. System is running good at this time of service. Explained to customer about thermostat issue and he is going to replace it him self