I can't seem to understand why may car aircon's thermostat stops everytime i stop my car for more than 10mins. Every glass and window starts to blur if i stop for few minutes, mostly at night. This means that it is colder outside than the inside right? the vent's are blowing warm air... and as soon as i start moving the winshield clears again and it starts to get cold again... this also happens in traffic though during the day the windows don't blur it's just like a heater... warm air blowing to your face from the vents.

Can anyone clarify why this happens and what i need to do to have it fixed so i know what to tell the aircon shop. thanks