I have a 2007 Cobalt LTZ that I am having problems with the air conditioning in. (I am new to this thread thing so I'm unsure if I am doing this right or not so please forgive if I am not)Anyway.....The check engine light was coming on and the a/c would not blow cool at times. I took it to Auto Zone and they told me that it needed a new temperature sending unit. We replaced that and it did correct the problem. The check engine light went off and the air has been working good until today. This morning it started blowing warm again and I noticed that the coolant was not showing on the info display. Now this afternoon it was working fine. Does anyone know what could be causing this? The dealership says that they do not know if it is something that is covered under the extended warranty.......I love my car...it's super cute...but it enjoys giving me fits....please help!! Thanks y'all!