No heat. Customer changed the time at the thermostat and , accidentally locked thermostat… I unlocked thermostat and inspected the system. Furnace is 4 years old only , and ac 21 years old, and works with r22(Freon). Heating is working properly, but due tot he age of the ac and being working with r22 (Freon), highly recommend to upgrade the ac system. For efficiency , humidity and savings in the house. Set a lead to quote upgrading for the ac in,y for Monday morning.