I don't use the rear a/c too much -- occasionally I enable it because my son gets a kick out of adjusting the air himself. Following that pattern, I pressed the dash switch yesterday, but no air flow fromt the rear unit -- however the rear fan and temp controls are adjusted. The light comes on for selecting upper or lower vents. The 30 Amp fuse ("Rear a/c") is fine. Is there something obvious or easy that I can check before taking it in for service?