I turned on the heat but only cold air blows out. How do I fix it?

Although not a furnace expert, I can tell that this question is too vauge.

Knowing this additional information might help:

What kind of heat is it? (Furnace, heatpump, space heater etc)

What is it's fuel source? (Oil, nat gas (or propane), electric, coal, etc)

How old is the unit?

Have you done anything to diagnose the problem?

If so, what?

And what were your findings?

Things like that.

Please write back!

Going to need some more info. Have you looked at furnace to see what is happening. Do burners come on at all. If they come on for a few seconds and then shut off, I would start by cleaning the flame senser (assuming you have a newer furnace) Or do you have a standing pilot furnace. If so, check to make sure pilot is still lit.

There are just to many things it could be. Please let us know the make and model of the furnace, and a lot more info than "it doesnt work" We will try our best to help. The best we can do at this point is try to help you trouble shoot the furnace. Do you feel comfortable doing this? Let us know.