Heater stop heating?

If your heater stops heating but the blower keeps blowing air, it could be as simple as low antifreeze level in the engine.

Let the engine cool off for a half hour.  Then add enough coolant to bring it up to the correct level.  Start the engine again and turn on the heater to see if it now heats.  You might have to run the engine at a higher idle speed to get it to circulate through the heater again.

Be sure to look for leaks when you fill it and when the engine is running again.  Usually, if the heater stops heating suddenly, it means there is a coolant leak some where under the hood.