No heat at idle 9C1 2007
 

I am a Sgt with a medium sized Police Department. Our Detecives use 9C1 Impalas.
Mine is a 2007 with 46k miles. I have had it since new.
At idle on cold days (I am in Alabama), the heater stops blowing warm air. The cooling system was flushed and filled by our mechanics last year, didnt change a thing.

Is there a TSB on this? This is really getting old........

Thanks,