So towards the end of last winter I noticed that my AC apparently had quit working when I tried to de-fog the windows. I didn't mess with it but when summer rolled around and I tried the AC it worked fine. Well now it's cold again and I tried to de-fog the windows last night but the system wouldn't turn on again. Does anyone know what could be causing this? Does the 134a expand when it's hot outside thus making the system think it has the minimum refrigerant level and contract when cold? I'm just wondering if I may need to add some 134. I have a 05' titan....thanks!