That is a good question. If your not getting any heat from the vents there are a few components that can cause this.
First check the coolant level in the reservoir and in the radiator (do this when the engine is cold or you could get burned by the hot coolant). Is it full?
Next when the engine is warmed up feel both the heater core hose. Be careful Both should feel hot.
There are doors behind the dash that open and close to allow hot air, ambient air, or chilled air through the vents; if these door(s) are broken or the motor that moves this door doesn't work will cause no heated air to flow.
A thermostat that is stuck open would reduce the heat stored in the cooling system
A water pump would be last on the list of possibilities.
Let me know what you find.
Thursday, November 14th, 2013 AT 6:41 PM