My 2004 Avalanche's A/C only cools the passenger side (55 F) . The two vents on the driver's side actually blow hot (150 F) air . This started after it sat at the airport for 17 days while I was on a trip. At times, the A/C will work properly at blow cold air on both sides, but then it may suddenly start blowing hot on the two left side vents. It has the base HVAC with dual slide controls. Any ideas of what might be causing this and how to fix? The intermittent nature makes it seem like either something is sticking or a bad connection somewhere. Not good when temps are in high 90's. Thanks in advance for any help!