the air condition works great.When it got cold out i tried to put the heat on and it blows out cold air I changed the thermostat and still the same problem.
Check the coolant level, and flow to the heater core. You can check the flow by seeing how hot the heater hoses are. If they are getting flow and coolant level is ok, then you may have an air pocket in the cooling system, these have a bleeder on the t-stat housing to allow you to bleed the air out of the cooling system. If this is ok, then you may have a faulty temp blend door, blend door actuator, or cable.