This just started tonight! I have a 2000 chevy tahoe 5.3 v-8 new body style. I noticed my heater does not work as well as it did before and when I am a stand still heater starts to blow cold air. Any ideas what that could be? I drove around after i noticed it and it kinda worked better but not to what it supposed to be! Any ideas or suggestions would be great!

 

You should take it in to have the cooling system checked . It could be a number of things .... faulty thermostat , rad cap , leaking engine gasket , etc.

 

Does the Heater start to blow hot after you get back on the interstate. Is your Check Engine light coming on and going off or staying on orneither.