2008 Mazda 3 wont blow hot air when in Idle
 

Hello I am very new to this actually i just made my acct but i have been looking and searching for someone that might know what is wrong with my baby!! I have a 2008 Mazda 3 it is an amazing car and this is its first winter so its the first time i have tried the heater. When i am driving the car that heater works great and blows really hot. But when it is just setting still idling the heater turns cold. I just had the water pump checked and its fine i just had a new thermostat put on and they flushed the heater core they looked at the coolant and decided they didn't think it was a blown head gasket and it doesn't blow white smoke at all the mechanics have no idea whats wrong and they are looking into it themselves so i figured id try this to see if anyone has had or is having the same problem. Please reply i really need anyones help i have already spent alot of money and it was all for nothing i don't want to keep waisting money.