No heat when idle
 

This is my third Sebring convertible...I just love them! I have a 2003 LX and when I am idling at a light or stop sign, my heat blows cold. It doesn't matter if the fan is low or high...it's freezing. But as soon as I start moving, all is fine. With temps here in the 20s, brrr. I read somewhere that I should check my coolant first. Any ideas?

the coolant is low and then u have a leak some where