Completed one system diagnostic. Found bad flame sensor not allowing furnace to stay on. Also found very dirty blower wheel that needs to be cleaned to achieve proper air flow. Capacitor for blower is weak as well. System has no water safety and no drain pan. Needs inline float switch to protect system and house from water damage. Thermostat is not working and needs to be replaced. Completed all repairs except float switch and signed customer up on maintenance plan.