My 08 GL450 climate control system is stuck on full defrost heat mode. It began with the blower turning itself on about 2 or 3 minutes after the car was shut off. This would cause a dead battery in the morning, however when the car was running, the controls worked fine. I could control the temp and blower speed, switch back and forth between heat and ac, vent control, etc. After a week or two of this, it began having intermittent trouble switching between temps, then all of a sudden the blower went to full speed and all controls stopped working with the setting seemingly stuck on defrost (heat comes out by windshield and side vents). I actually tried a different control head that I found on EBay with the exact same behavior. Is there a relay or computer module that could be causing this?