Ok guys, I've seen the threads about HVAC problems indicating a bad thermostat (no heat in the cabin). The problem with my 06 3.5 is no heat when you stop at a stop light, but when you maintain speed (40MPH+) plenty of heat. What gives? Next question...where is the thermostat and how hard is it to replace?

 

Sounds like a low coolant level.

 

I second the low coolant...if it is good, I would flush your cooling system