Heater blows cool air?

[soupy]

My 2005 Grand Prix 41,000 miles is blowing out cool air. If I set the blower on a low setting it blows a little warmer. Any suggestions? Only maintenance thus far is routine oil change and new tires and rotaions. With such little miles I have not done any other Maintenance.

Thanks,
Ken

 

[soupy]

I forgot to mention that the engine is not over heating or anything. Temperature is normal.

 

[stealthee]

Is there enough coolant? Is the heater core blocked?

 

[eleedy]

Same sort of thing happened to me today, it came out hot as could be while I was driving, but sitting at a red light it came out cold. Turned out I was low on coolant and it's been fine ever since.

 

[soupy]

Coolant is fine. How to I check if Heater Core is blocked?