Hi I'm Mike. My wife's fiat Palio heater does not work, its just blowing cold air what could be the problem

SOURCE: 1997 audi A4 heater blowing cold air

You will have to change the heater core. 9 out of 10 times, when the heater is not heating the air, it is a bad heater core.

SOURCE: 2001 malibu-heater is blowing cold air

sounds like you have a bad temperature sensor in dash or the cable has eitehr broken or come off the heater switch under the dash!!

SOURCE: overheating, blow out through exspansion container

note that thermostat and water pumps eare both part of the cooling system you neded to ck them for proper fonctioning .,ck the radiator fans electric motors for blowing propely ,ck radiator for clogs in the lines ,hoses for leaks ect.......

SOURCE: heater blowing cold air

squeeze the hoses to get any air bubbles out and refill coolant as necesary. are you sure you put thermostat in the right way? may be backwards. also may be your sensor.

SOURCE: heater only blows out cold air

Check the valve that controls coolant flow to the cabin